I am mildly curious as to whether this is actually against the rules.

Thus far, the rule on alts have only been "not helping main".

And if it's non-alts, I'm sure you are allowed to be as deliberately annoying as you can.

I guess in a round-about way this can be used to help main via helping main secure victory by suppressing competition. But that's rather round about and hard to prove.

I mean I don't agree with the practice and would like to see it being banned. But, is there even a basis for any admin action even if you could prove your case? It could potentially come down to subjective interpretation of rules, I wish rules could be more strict than subjective.