Andrew Anthony, having a healthy online debate with Sunny Hundal:

Your post reminds me of Conor Foley’s first posting, insofar as they both seem primarily interested in proving their nuanced credentials

One feature of online discourse is that very little is taken for granted. A blogger (especially one on a highly trafficked site like Comment is Free) has to cater for all persuasions.
In practice, this means you have to add more information than is strictly necessary to advance your message. Either that, or risk getting lost in the minutae of a debate that distracts from the new and interesting point you were trying to make. I don’t think Sunny was trying to prove anything by citing his ‘credentials’. He was merely citing certain previous examples of his writing, in order to head off fairly the obvious counter-arguments.
By contrast, I think print newspaper columnists and authors have a general idea of who their audience might be, and write accordingly. If you can be sure that your readers all share certain values, and accept certain arguments, then you feel confident about jumping into the debate several conceptual steps down the line. This confidence is shattered when you enter a world where responses are immediate and unfiltered by a Letters Editor. Authors are left with the impression that the readers are impolite, uncouth and agressive.
I actually think a great deal of ‘fisking’ is redundant for the same reason. Since the blogger does not share the same world-view as the columnist the target, a line by line rebuttal never seems as effective as a stand-alone composition.
There is a well known phenomena of bloggers suffering ennui with the medium, eighteen months or so after they begin. I am just emerging from just such an affliction now (although since I post at a relatively low frequency I doubt either of my readers would have noticed). I think much of this frustration is a result of never getting to the nub of the argument, never quite managing to debate the subtle point one wishes to make. Instead, the discussion is dominated by the clarification and vocalising of preconceptions and core values.
This worry passes, of course, since the core values are either reinforced or abandoned by the scrutiny. Blogging is a process of clarification as much as anything else.