Posting screenshots from other boards, especially closed ones, are not ethical at all and should not happen.
Says who?
I do Peter
Well, I don’t agree.
I would argue that hiding a board is unethical. In future maybe when you want to have a nice b1tching session do it over PMs.
You are entitled not to agree.
It is a closed board not a hidden one.
I would suggest that taken a screenshot on a closed board and then posting it on an open forum that anyone can see is very unethical and underhand behaviour.