I've created a comparison chart and lists of features of different online writing communities. Please feel free to share if I've missed anything. 

Writer’s Cafe

• Offers stats

• Offers a wide variety of in depth, free courses

• Has features to search for literary agents, publishers, and literary magazines. They also recommend several different self publishing services.

Critique Circle

• Users are on a “trial” account with restrictions when they first join until a moderator approves their application.

• Credit system earns points by critiquing.

• Critique queues last a last before they switch (there are five types of public queues). Queues work by number of critiques, waiting length to get into a queue depends on number of critiques that week.

• Premium members can create their own queues.

• Newbies get special queue (newbie stories can only get six critiques, but other queues can have an unlimited amount), and can ask a moderator to evaluate their critiques. They also get a special page for a month.

• More than one story in queues at a time will cost more credits.

• Once a month, “hook” queue for story beginnings.

• Receiver can evaluate a critique. Critiques receive an average of the evaluations of their critiques for every five critiques they give. They cannot see personal evaluations.

• Must be logged in to see stories.

• Different levels of story accessibility.

• Accounts automatically deactivated if no login for six months.

• Stories are removed if they are over a year old. They are archived and a specific file is sent to the author which can only be read by uploading it back to the site.

• There are three types of critiques (Template, classic and inline) and critiques are autosaved.

• Critiquers can send private critiques to the author.

• Other critiques can only be read once it has been critiqued and archived.

• Erotica and esplicit sex cannot be displayed publically.

• Published or soon to be published stories cannot be posted.

• Full manuscript critiques allow a manuscript to be downloaded, and an author can pay them credits for the help.

• Activity ranking

• Quality + quantity critiques can get a free pass (plus keep multiples) to have stories bumped up in queues. Premium members can buy free passes for 15 credits.

• Allows printing

• No age limit

• Users can blog for CC

• Premium members can create private forums, showcase their works outside of CC, and have access to a Novel System that allows them to string their submissions together.

• Has a Notebook feature for planning (limited for basic members)

• Displays for Manuscript Progress

• Can connect to Amazon books

• Outlining Workshop for characters (basic members allowed two, premium unlimited)

Mibba

• Offers blogs and magazines

• Tutorials on lots of different subjects

• Special section for reviews and articles

• Lots of forums

Figment

• Merged with HarperCollin’s “Inkpop”- Now owned by RandomHouse

• Mobile App

• Has comments and reviews (although mostly comments)

• “Hearts” another name for “votes”

• “Early Access Codes” - Personal URL links to hand out to select readers

• Offers badges for accomplishments

• Story “reactions” (laugh, wow, and cry)

• Can be used for educators in classrooms

• Public and private groups

• “Chats” with published writers, editors, and professionals

• Offers polls and quizzes

• Target market is more towards teens (posts a specific crisis hotline page), site is known for immature users and drama.

FictionPress

• Sister site to “FanFiction.net”, offers only original, fiction works

• Wide variety of genres, including poetry

• No copy paste on stories

• Beta readers allow for more in depth critiques

• Communities for custom archives

• Can change font style of site as well as language

• Offers a mobile app

Booksie

• “BooksieSilk” is the sister site for mature, adult content

• User “portfolio” including a micro-blog/journal and a page for published works

• Can upload audio recordings and podcasts

• Books (previews of published works, 1 chapter) vs Novels (multiple chapters)

Scribophile

• “Spotlight” is a list of works that are being featured. There are four types- Main, New, Good Critiquer, and Personal for premium members. Each spotlight has different rules and depends on number of long critiques.

• After a work is featured in spotlights, it is only open for 30 days afterwards, then it is locked and cannot be critiqued any longer. Works can be unlocked for 5 karma points.

• Features a “Karma” system that reflects works posted vs contribution to community/reactions to critiques.

• Features reputation points for users

• Groups

• Premium members can include images in their works

• Quotes are used in critiques in a specific manner, karma can be cheated by quoting wrongly

• Features an Academy

• “Writerfolio” (Portfolio for writers)

Protagonize

• Dedicated to various forms of collaborative, interactive fiction

• Features Addventure writing (RPG style)

• Portfolio style author profiles

• Offer collaborative works called “branches”

• New postings can only be changed for 24 hours unless the original author allows it

• Has a section for author notes

• Can split chapters into a new work

• Author Guidance allows original author to put in  extra story information

• Also allows solo works, which are not collaborative pieces

• Allows for printing of projects

• Authors who are reported for misbehavior are disqualified from top rankings if the matter is unresolved or found serious enough by a moderator. Also publicly broadcasted.

• Special groups feature

• Profanity filter

• 140 character minimum for story lengths

• User and story Statistics

• Editor Picks and Feature Author/Groups are for selected members to showcase their work based on quality, activity, and other factors.

• Allows for recommendations.

• Allows friending and subscriptions to favorite authors

Wattpad

• Status updates

• Broadcast messages to followers

• Private and public messages

• No friends (followers instead)

• Ability to dedicate a chapter to another user

• Votes per chapter (how much you liked the work)

• Story comments have a WC limit of 2,000 characters

• Story statistics

• Stories feature:

  • Pictures, web links, and videos

  • Easy to share

  • Story ratings

  • Public vs. Private chapters

• Strict about sharing your stories on the forums

• Lots of forums/genres

• Book clubs to meet new writers and get your work read and commented on

• “Magazines” published by users

• Can follow published authors

• Read classic books and other non-copyrighted writings

• Public and private libraries

• Mobile app allows you to change the page color

• “Kickstarter” (crowdfunding) for books/projects (complaints that its only for popular writers)

• Experimenting with “extra” content as in paid bonus chapters after a story is completed.

• Features awards and many publishing contests

• Many popular stories have been published.

Inkitt

• No book covers, instead there are specific 1280x420 banners on the top without text.
• • No ranking system
• • Stories are "curated" every 24 hours by staff
• • Features several basic forums in a post/comment style
• • Profiles feature basic profile picture/banner
• • Sleek, modern look
• • Stories are read in full browser and feature a variety of reading adjustments including text size and page color
• • Stories feature chapters, titles, a 200-character summery, and chapter titles
• • Rating limit for children, teens, and adults
• • A main genre and a subgenre
• • Story statuses, and language option, and tags
• • Stories can be entered into contests where they are voted on by members
• • Reviews have no word limit and feature star ratings
• • Users follow/friend other users by adding their stories to their reading lists
• • Has a copy paste block

No Longer Exists: Hexbound (Now Valorpen), Authonomy, WriteOn