It's a bit up to debate as to whether it was tactics or just traffic (as Hamilton had Bottas in front as well so had to leave room).

Has slowing your opponent on purpose in qualifying done before? ABSOLUTELY, the most memorable for me was ironically actually on the same track in 2007 when Alonso purposefully held Hamilton in the pits so he couldn't go for the last lap and Alonso secured pole. It's a very famous incident and Alonso got penalized.

Will there be retaliation? Probably not in a direct sense, F1 rarely have such actions except for very notable incidents like Suzuka 1990 at the first corner. It's very rare. I mean the biggest retaliation would be to win in your opponents face square up.