Ran into an issue for the first time yesterday since I've started playing ranked a few months ago.
Long story short, joined the ranked lobby, realized after a bit that I couldn't see two players' chat, and couldn't see it also in game. Ended up remembering I blocked one of the players due to past trolling and concluded the other guy was in the block box as well.
Mind you, it takes a lot for me to physically block someone (ie, press the little button post match to block). I was matched with the player I remembered several consecutive times in casual conquest, and after multiple games of trolling and continued tower diving, I just blocked him. I do not immediately block someone after a bad game; people have bad games all the time.
I thought blocking a player reduced chances of getting paired with said player? If not, block should not limit in game communication, that's what the mute button is for.
TL/DR: If blocking a player does not keep you from matching with said player; it should prevent communication outside of game only. You should be able to communicate with said player in game, and the mute button should only mute for the duration of that game only.