It would up to the moderators of the community doing the following to follow communities that abide by the same rules. If a post on the followed community broke a rule, I think it is obvious that the instance following them should have zero say over what is done. If they disagree with the moderation of another community, then they shouldn't be following it.

I do think in many cases this would be useful on reddit as well. I assume r/truegaming was made to separate themselves from r/gaming, but I don't see why it wouldn't make since for r/gaming to follow r/games and vice versa, unless of course they have differing rules.

I believe you can moderate a community on/from another instance, so it would be logical if, when agreeing to mutually follow each other, they also agreed to add mods from the reciprocating community?

The Reddit example could have worked the same, but the sub due to scale the equation is different and the benefit of the increased community size is less and the Reddit mods would likely see little benefit Vs the dilution of mod status.