What sparked this question is that I'm still getting an awful lot of comment spam. Almost all of it gets caught by my moderation system (which sends all unauthenticated comments on old entries to moderation), but then I have to page through hundreds of spam comments a day to see whether any legitimate comments have been filtered. Sometimes I fall behind, and interesting or important comments languish in moderation for weeks.
I could start using a system like Akismet, but despite having heard good things about it, I'm reluctant to trust a spam-filtering system that I don't have direct control over. (This is entirely me being a control freak; I have no reason to distrust Akismet or any other antispam system.)
And then it occurred to me that spambots probably generally don't have JS enabled. So I might be able to do JS detection and just not show the comment form to anyone who doesn't have JS enabled.
But if it turns out that some of y'all who comment on my site don't use JS, then that wouldn't be a good idea.
Note that if you comment on my entries on Facebook, this entry is irrelevant to you—I'm only talking about people who post comments directly on my site.
. . . I may just decide to try this out, as an experiment. So if you try to comment on a recent entry and no comment box appears, and you think it may be JS-related, drop me a note in email.
. . . Heh—Most of the way through writing this, I tried turning off JS in my own browser to see if I could still comment. But of course the Movable Type entry-writing system relies on JS for various things, including auto-save, and so I lost several sentences of this entry. Not a big deal; I restored them. But kind of ironically funny.