There are some weird edge cases, like sometimes a banned user, once they're unbanned, will revert to posting abusively. Then we ban them again and they revert to posting good comments again. Who can fathom the psyche of homo internetus.
It's also common for an account to post both fine comments and abusive comments. It's the latter that determine whether we have to ban the account—that's how rule enforcement works. But if a banned account posts something good, there's no reason why the good post needs to remain [dead]. This is what vouching is for: https://news.ycombinator.com/newsfaq.html#cvouch.
I'm going to contact the moderation indeed, it's the first time I was seeing non-spam comments being shadow banned automatically.
The behaviour of the account holder.
Unfortunately we don’t and we just have to trust dang and the benevolent hacker news gods to always have our best interests at heart and only spam us with the content that they want to spam us with and of course their friends and insiders content which we should be grateful to be spammed with.