Dear Gustavo, yes KDE bugzilla needs a user agent and the curious things you get are from the time where KDE used debbugs to track their bugs.

FWIW I've been scripting for bts-link on many bugzillas installations, and KDE one is one of the oldest bugzilla around (which is a pain for many reasons I wont elaborate about here). But AFAICT, the User-Agent: restriction is quite common. It's a usual thing that you need to have a proper 'Accept: */*' line as well. Some bugzilla have such complicated sets of restrictions I've not been able to deal with, that bts-link spawns wget to fetch pages sigh.