I've done it after holding a darkage all-in where my opponent was bantering in-game. It was chill and we GGed before leaving the lobby. Haven't had a match where it felt right since.

Whether it feels appropriate depends on context and reception. In most situations a random AOE4 player you meet on latter will be uncomfortable with it and will take it as an insult instead of as banter, so I refrain.

On the other hand, I play fighting games, where trash talk is often celebrated, and the context supports it better. If I'm playing a Blazblue set with somebody, there are breaks between each match to chat and build rapport so it's easier to establish that we can make jokes and talk shit without taking it personally. It's hard to build that in an RTS when you and your opponent are hyperfocused for 40mins straight, then have one brief moment to chat in the postgame lobby.