It happened to me twice this day, one in the middle of the match, and no was not afk, i was literally walking.
The other one at the respawn at the beggining of the match on the countdown.
For real, blizz need to keep an eye on this, you should get kicked if you are inactive .
Did you say anything in chat? Where were you walking at?
Did someone report you afk and you had to type /afk to remove it?
Did you click on a table portal before the match started?
Oh yes, why?
You got trolled, typing /afk makes you afk and kicks you from the bg. If some random played sends you a message telling you to type that they are messing with you. Probly trying to kick people out so a friend can join.
Na i clicked on a mage portal, the second time i don’t know .