[...] What few know is that the mobile sites don't follow the standard
permission system: instead, they override permissions and prevent
unregistered users from editing at all.
I propose to remove this exception to the rule, which was meant to be
temporary and looks now technically unnecessary. Unregistered users will
be allowed to edit on the mobile subdomain for a wiki, if they are
allowed on the main domain. [...]
The discussion will be open until 2015-03-15. I'll send wider
notifications in few days. In the meanwhile, sorry for the crossposting.