This thread is in meta, so I will answer from the perspecive of forum policy.

For any question about allowing alt accounts doing x, the answer is yes this is allowed. The only exception to this is when someone is banned, as the offical policy is to not create an alt account to evade a ban. In practice however, if you are evading a ban, and are not otherwise causing problems, you will most likely be ignored. The most profilic trolls and spammers will have more resources put into finding and banning any alt accounts when they are banned.