I definitely agree with the speculation part. Not knowing a reason for any form of ban (temporary or permanent) can be problematic especially if the user in question has been contributing positively prior to the ban. In that case it would be normal for users to ask the moderators questions which as you said might receive a reply.
If there could be a moderators thread which they can use to list users that they have banned citing the reasons, it will allow for there less speculation in the general sense. With moderators not really commenting on or replying to questions about banned users, it has the ingredients of causing disharmony simply because of the lack of knowledge surrounding the issue especially when the banned user creates an alt-account to push through their own attempt at unbanning. You are right when you pointed out there are not many ban appeal cases therefore I hope it is something moderators would consider in future.
I do think that using an alt-account to send PMs trying to appeal to certain members to post (in favour about having their ban overturned), is certainly not good form.
That was what I was thinking, the moderators are not under any obligation to provide explanations when either temporarily or permanently banning a member. I think I have only seen one instance (not the one you referred to in the Croatian board) where a moderator might have made a comment but they do not give a running commentary.
That's one of the rare things I don't like about this forum, that mods don't answer on such threads. I do understand that no answer is also an answer, but it would make people speculate way less so instead members talking for years (like in RegulusHR case), they could just give a simple answer and end the conversations. Its not like there are many ban appeal cases anyway.