If admin disable signatures in boards not related to crypto, we will see an increase in activity in crypto related boards for sure.
This could be an idea to reduce posts about offtopic discussions
I agree that disabling signatures would only move spam to another part of the forum. It's not a solution. I am not even in favour of any kind of "punishment" or labelling of those who did not write about technical matters.
I'm more in favour of some form of rewarding those who have contributed to quality. For example, every month, one or two "highest quality" members in that period would receive a temporary quality badge and an additional +10 karma points. Of course, the karma system would have to be improved for rewarding karma to have value.
Also, creators of quality themes should be additionally rewarded, with points, badges, whatever. Later such points could be converted into ALTT tokens. That would certainly help