I think the others covered this fairly well, but I’ll add a little blue to the reply.
Yes, accounts may receive a temporary suspension if they are found to be /afking in Battlegrounds but it is important to understand that the findings for that are based on data, not reports. Just because you are reported as /afk doesn’t mean anything will happen, very much like being reported for cheating, if the data doesn’t back up the accusation you’d never know that the matter was looked into.
It is also important to understand that a penalty for /afking in a Battleground isn’t for a single occasion. It is based on repeated occurrences.
Generally not, no. We tend not to penalize someone for reporting another player. The other player may have believed you were /afk and calling attention to it. Those submitting a report are allowed to be wrong, we don’t wish to discourage people from reporting potentially damaging behavior for fear of reprisal if they aren’t 100% accurate.