The method of logging in to this forum is out of our hands. It's part of the overall design package. However, it isn't strictly necessary to log out . Many folk just move off the forum without logging out. I don't know if this is possible if you are using a phone however. I've never tried.
Regarding your second question, you won't get barred from this forum for your thoughts and comments but I wouldn't recommend you try it at the other place. It's not unusual to have more than one forum dedicated to the same subject for example, VW or BMW.. There are two forums dedicated to Eribas in France, also the same in Germany and Portugal.
Randa