Thom27: I guess it's the same effect as we discovered before with capturing an opponent's spy; if (in the same move) you place a piece next to the spy before capturing it, that piece will become visible for the opponent. As long as you know that it's no problem since you can avoid this by capturing the spy first.

What you mention seems to be unavoidedablt by your opponent. They won't even know you know what you captured. This seems to be a bug to me, does everyone agree on that? I suggest we should report it.