It is obviously allowed to discuss Linux. There is plenty of discussion about Linux on Facebook, including some about the recent "ban".
My guess is that some automated scanner found something wrong about the linked page. Maybe there is some link to a "hacking"-oriented distro, maybe some torrents, some dubious comment, etc... Probably a false positive, it happens.
It is obviously allowed to discuss Linux. There is plenty of discussion about Linux on Facebook, including some about the recent "ban".
My guess is that some automated scanner found something wrong about the linked page. Maybe there is some link to a "hacking"-oriented distro, maybe some torrents, some dubious comment, etc... Probably a false positive, it happens.