Today is not beautiful enough for me. I was surprised by a few things on the forums that I thought I understood. I found something strange again. I think so

2] Does he delete all posts and activity will go back to the beginning?
3] If I'm not mistaken, he should at least be a hero member
4] Is this normal? or am I the one who doesn't know about phenomena like this?
This account registered on 2013 and the merit airdrop was till the end of 2017 so he got 500 merit as per his activity and became a Hero Member but maybe he deleted his post and that's why his activity decreased and also his rank decreased and now he is in Member rank.
1. Deleting a post reduces the activity and it can go down to 0 no problem
2. Once merit is added to a profile, it is never deleted. If activity and post count is 0 then merit will not decrease even 1