How can I level up? How can we unlock other levels? I mean, I don't want to be a ''Regular Member'' anymore.

Since I'm a moderator, I can assign users to some User Group.

There are 3 groups actually. Administrator and Moderators (EmperorTigerstar, Drex, Me); Regular Users (everyone else including you) and losers (People that misbehave too much).

If I think some mappers here deserve to "rank up", perhaps I'll create a group for those people.

But don't be fooled. Your recent misbehavior both in the comments and the map post will not make you rank up. I'm warning you. If you continue to misbehave, you will be de-ranked to losers, or even be banned.