Alright, now I know how he knew all my private messages.
He just knew my account details.
Perhaps he got them when I clicked the link to the site that imitates bitcointalk. Dunno how he did that, but fortunately I have changed my password right away after I saw that I got to the dangerous site.

Here is one more email from this guy:
https://imgur.com/a/cHBCfxp
where he provides my username and password.

Now guys. I do not know if this email belongs to OgNasty. It seems to, but I'm not sure. He was surely involved in all this, as he gave me the negative rep. And his real account gave me that rep, 100%. You can see it by clicking in the link of my profile and then going to my Trust.