I switched to Linux and I am using Brave (browser).
I never had an issue like this but when I go to post a thread, I get logged out. The same with making a reply. It doesn't happen every time either. It is really confusing. I couldn't figure out what could be causing it. My posts seem to be going through regardless but I figured I would mention the issue. I didn't have this problem when I was on Windows and Chrome. Though I did have the issue where I was appearing logged out on the main page. Maybe it is part of the same issue but a different variation of it?