I responded to one of the posts in that thread (in this message: http://aspn.activestate.com/ASPN/Mail/Message/modperl/2176383) just to try and clarify our position here. I'll see about updating the kbase to be more clear... we're not saying that mod_perl itself is bad (quite the contrary - our whole web panel is written in mod_perl) - however the fact that poorly written code can cause problems in a shared hosting environment means that (in our opinion) mod_perl isn't well suited for use in that environment.
Anything where one user's actions can potentially take down literally hundreds of other sites is something we like to avoid.
Also, we simply can't support everything we'd like to support, or everything that some users want... if anything, I think we're maybe too nice about this sometimes already. While features are important (and bring in new customers / make existing customers happy), ideally we'd like to strike a balance here - providing useful features AND providing reliable and stable service... maybe tilted a bit towards the latter.