I seem to be mistaken. However I was twice as stupid because I have hidden all these messages, and now I can't recover them on my timeline. I don't find them in my activity log (not under "hidden" nor "all"). Strangely, if I update my status and make it "hidden" in my timeline, it shows under "hidden" in the activity log...

Likewise.

Well, FB had kind of jumped the shark. I guess they wanted to leave no room for doubt about it.