I've used Teams for the 1st time today (on Chrome), since it's the platform used by my employee to run the online training for the job. I've been in the room together with 26 other people, most of which were using Teams for the first time, as well.
1st suggestion: You should have an animation confirming a participant can be heard. We were all having our mics switched off, and had to raise hands to be able to turn our mics on and speak. Many would first ask if they can be heard, whereas an animation (e.g. that classic zig-zagging line) would've been enough to know the audio goes through.
Many forget to lower their hand, after being raised, and the group chat leader can be confused as whether someone actually wants to talk or simply forgot to lower hand. Perhaps it'd be better to have an easier to notice status for that hand icon...
- bring hand towards the bottom of icon when down, towards the top when up
- display hand up when it's up, and flip it vertically when down
- make the icon bigger when hand is up
- or, when chat leader selects user X to speak, leader hears user taking his / her turn to speak, user's hand is no longer needed to stay up, leader can click on it and lower it for the user
... or the user gets an overlaid center button saying "lower hand"?, so that he / she cannot forget to lower it... etc.
While in the chat sidebar, maybe people who raised hand could be indicated next to their last message, so that they can be spotted without having to flip to the chatroom users list. Better yet, have a mini-list of people who raised hands appear at the top of the chat column (and a blink icon). Or at the bottom, under the text input field (lifting the chat window). It's usually 1 or 2... 3 users? 5 users... lifting hands. IF there are more, then "more" is displayed and chat leader will then go to chat users list.
If there are just two, or three... they're little enough to be displayed in the chat-room so that chat leader can stay in the chat window and know who raised hand without going to users list.