Blizzard started monitoring audio chats to fight toxicity as part of their Defense Matrix system for Overwatch 2. The audio transcriptions are scanned only in a few countries so far, states the official announcement from the developers.
Blizzard promises not to listen to these chats and to delete the audio recording afterward. However, they will keep the transcripted files. After a player reports bad behavior, the system creates those automatically. Also, Blizzard states that it won't monitor group party chats at all.
They didn't specify which countries will be monitored. Most likely, they chose English-speaking states since it's easier to test the results. For example, it was how Riot Games did it during a similar anti-toxic system launch earlier this summer.
In other patch changes, Blizzard tuned matchmaking algorithms to estimate players' levels better. They promise that "these will become even more noticeable at the start of Season 2". The developers also added aim assist for crossplay lobbies. It will work everywhere, except for the competitive mode.