It can be good sometimes to discourage off-topic comments
and stuff. I received a negative reputation on a
comment I made a while back, which
is fine, because it was kinda off-topic. IMO, the comment
I replied to, was too, but that's another story. :)
Yes, discouraging off-topic comments and stuff is good, if you, the posting monk, _know_ why you get negative reputation. But I still think that kindly telling (commenting) the posting monk of the comment/question/stuff _what_ is wrong is a better approach.
/t0mas