This is, for the moment, purely hypothetical.
Say I am a moderator on sites A and B. On site A, a user behaves somewhat rudely - not enough to warrant a suspension or anything, but still clearly breaking the "Be Nice" policy. The matter is eventually cleared up. Later, on site B, the same user behaves rudely once more in an unrelated incident - again, not rudely enough to warrant a suspension, but still behaving inappropriately.
Let's imagine - for the sake of argument - that there is enough to warrant a suspension if the actions had been committed on the same site, because it was a repeated offense that could not be let go. However, the actions were committed on multiple sites.
The actions, however are limited to these two sites.
What should I do? Suspend the user on both sites? Neither site? Is there another option?