The two way conversation web just got a new player, after the ad hoc comment blogging hack piggybacking atop Del.icio.us as a public data repository backend, Commentosphere doing the same with a more custom crafted Ning playground backend and allowing for a bit more semantical data stored about comment threading.
Where these hacks have largely been a manual business for the end user, but which works across the entire web, coComment has gone the other way about it, and covers only a select few blogging platforms, presumably growing over time.
My own approach landed somewhere in the middle ground between these routes, starting from the manual though deadly precise Del.icio.us comment blogging style, partially automating the process for Blogger blogs with a Greasemonkey hack of mine. I did not move on to cover other platforms, largely due to a lack of ambition combined with my high expectations about getting good permalinks, to the very anchor of my comments -- so I can easily find and link to the spot on a page where I wrote something.
In this respect, coComment does not go as far -- it presently only picks up the comments you write and tie them to you, integrating the data with a few services for syndication and the like from their own site, where you can also track conversations by other members running the same system, and blogs where the blog owner has crafted his comment form to also run incoming messages by the coComment repository. There are lots of plans and high hopes about the kind of things we will be able to do with the coComment site and it's data, though, and they seem set on extending their coverage to a larger platform set, and involving external contributors who want to take part in helping this thing fly. An excellent combination.
At the coComment base site, the service is rather similar to off-site comment layering frameworks such as Hoodwink (where comments never actually touch a destination blog, though, but rather hang somewhere on a side server for people who opt in on the comment network's data only). Members may browse the site, fetch RSS feeds for their comments or those of other members. At present, these feeds are not as customizable as those of i e Hoodwink, though, where you may browse by any combination of blog, comment author and discussions where a particular author has taken part. They unfortunately only store (or present, at least) comment text though, so any links and similar HTML features of your comments are shaved off at the moment. I suppose it's time I head over to their feedback pages to share some user input.
To become a member in the beta program, you need to ask for a code to be let in, but said code is at least now sent out within a few days of your asking for it, so the hurdle isn't very high to leap.
Technically, the coComment implement their service using the cross browser, though laborious way of the browser bookmarklet. Brian Benzinger, apparently sharing my belief in automation through user scripts, made a Greasemonkey script for automatically injecting the coComment hookup code on blogs supported by coComment at the time. Not quite happy about a script I'd have to update (and find out when to update) manually as soon as coComment added another service (in the short time since he wrote it, they seem to have covered Flickr too), I cooked my own, which updates itself daily from coComment (userscripts.org entry).
It detects injectable pages the same way the bookmarklet injection code does (using the same ruleset as found in today's version of the injected code), but it appears it might need tightening up a bit not to inject on all pages matching those criterias -- the common Blogger post editor seems to be recognized as a comment posting facility, too. It will be interesting to see whether this post shows up in the system or not.
I just tailored my user script to exclude the blog editor from processing, just to be on the safe side, even though coComment did not actually seem to pick up anything on my posting this entry. Feel free to give a shout if there are any other pages on other blogging systems where I ought to do the same thing, by the way. Don't forget to include the full URL(s), so I can update the script accordingly.
And to coComment: feel free to use and promote this script for your user base. It works with Firefox, does not work with Opera (since Opera does not implement any persistent user script storage such as that offered by Greasemonkey's GM_setValue / GM_getValue), and it might work with Internet Explorer running Reify Turnabout. Installation is about as easy as the bookmarklet installation, the work on your part is as low, and running it is trivial, beyond even needing documentation.