Okay, this is something I suspected: after my fresh install of the new OpenSUSE 13.2, I came to find out that pidgin 2.10.10-5.4.1 installed from the new distribution works OK again (connects to Yahoo, and I can use it as normal) ! Strangely, without any clue about what was wrong with older pidgin from OS 13.1 (just before installing OS 13.2, I had used pidgin 2.10.9-4.18.1, as the latest version available for OS 13.1) :( Well, that being said (written), this bug I don't know if we can consider it solved.