What is abusive ?

[thejeff]

It also ignores bugs they haven't been able to track down.

And any house rules for a particular game should be honored, even if the game doesn't/can't enforce them.
I think the default, if informal, house rule for games on this forum includes "don't exploit bugs on the bug list"

There are also metagame abuse issues that can't be addressed by the mechanics. Host setting up a map to favor himself. Secret pre-game deals. Playing 2 position in a game. etc, etc.