I'm not advocating for self-voting, just to be clear, but if it was really against the community rules, the ability to self-vote could have easily been forked out long ago.
Good point.
The rule is that there are no rules and everyone can do what they see fit. The argument is "if you don't like it, you can walk away". So, that is, what people usually do. It keeps the playground small.
The space here is paradoxical. The usual players tell you that they don't appreciate the drama and someone publicly mouthing off about voting practices and using tagging would cause such useless drama. However, I think it's a lie and drama is exceedingly appreciated as an opportunity to demonstrate one's power. Happens regularly in a kind of gleeful way.
Personally, I think tagging is superfluous. If I have something to say directly to someone, I go to their blog or comment their comments.
Conversely, there is no fierce objection to tagging if the blogger praises someone tagged. LoL.
So, regarding self voting it just depends on whim, mood and who is reacting to whom on such basis.