I got asked why I turn comments off on older posts - "older" meaning anything that's aged off the front page (and out of the feed). Well, the simplest way to explain that is a snippet from a log I keep of spam attempts on the server. Not a lot of detail here, but here it is:

<<< Matched Against: insurance-ratings >>>
<<June 5, 2006 10:43:45.330>>
<<SPAM: Text Match>>
<<June 5, 2006 10:43:45.455>>
<<COMMENTS OFF>>
<<June 5, 2006 10:43:45.665>>
<<COMMENTS OFF>>
<<< Matched Against: insurance-ratings >>>
<<June 5, 2006 10:43:46.428>>
<<SPAM: Text Match>>
<<< Matched Against: insurance-ratings >>>
<<June 5, 2006 10:43:49.477>>
<<SPAM: Text Match>>
<<June 5, 2006 10:44:39.131>>
<<COMMENTS OFF>>
<<June 5, 2006 10:45:05.746>>
<<COMMENTS OFF>>
<<June 5, 2006 10:46:04.345>>
<<COMMENTS OFF>>
<<June 5, 2006 10:46:08.027>>
<<COMMENTS OFF>>
<<June 5, 2006 10:47:26.502>>
<<COMMENTS OFF>>
<<June 5, 2006 10:47:44.774>>
<<COMMENTS OFF>>
<<June 5, 2006 10:54:42.368>>

The "COMMENTS OFF" bit shows that someone tried adding a comment to an older post. I have the content saved in a directory - it's all spam. The text match lines show matches against my black-list, which is a simple text file of "bad text". That catches an amazing amount of crap too (I use the same approach on the Wiki).

Anyway, this is why I turn off commenting on older posts. It would be too much for me to keep up with, adjusting the filters. I have the ability to leave comments open on individual posts, and when I do that, I get a post specific feed (which allows me to monitor it).

I also use a simple "too many hrefs" filter - I figure anything that comes in with more than a small number of links is junk (and while that has snagged a few good posts, it mostly catches link laden spam. Anyway, that and an IP throttle, and I catch most things. I'm getting tired of the trackback spam - I rarely get actual trackbacks. I may just turn those off completely.