I am currently logued with a user without any special permission on the site (just a user which does not belong to any group expected guest).

Once logued, I could access to the toolbar in order to access to MySettings, etc... Frankly speaking I do not see the interest to display such a toolbar for logued user whitout any edition permissions. Currently there is a role in the admin center in order to hide such a toolbar for read-only or UGC logued users. But you need to group all these users into a group which does not exist by default (e.g: UGC_users or something like this). Another option would be to automaitcally display the toolbar only if one logued user has a RW or RWA permission on the site. I do not know if such a check is possible. But this would prevent to load hundreds of kb of useless Toolbar JS code by default. And finding such an option is not so trivial. We even did the fault ourselves on jahia.org, that's to say....

Coming back to the bug, the language switcher is displayed in live mode with:
1) language which are not published yet
2) workflow state which should only be visibile in edit mode.