Well, I can't see how the IPs would get them anywhere close to useful information.

So, if they seriously thought the IPs on the email were not anonymized, they could say, "Hey, does this IP match one of the IPs on wank_report?" And let's imagine it does. What do you get from there, unless there's enough information in the anonymous post to identify the person involved. If you're matching an IP to a post by someone who's logged in-- there, at least, you can say, "Look! It matches! Aha-- it was you!"

Still, even in that situation, IPs are largely worthless, unless someone has a static IP (or one that remains static for months until the router is reset, say). Quite a lot of people have IPs randomly selected from an available pool. In which case: they probably won't match anyway, even if it's the same person.

Basically, unless you get a match really close in time, or multiple matches over time (like Scotch, for example), IPs can't tell you much of anything.

(It can be really funny when people start arguing with themselves or asking themselves for more information, though.)