Same on GN sometimes, but you're right - not our place to criticise. I always have a metaphorical red pen in my hand, but use it metaphorically too!
I do have a lovely little group of ex students on FB - all now in their 40s - and they love it if I tell one of them off, and revert being 16 in an instant.
FB is certainly an eye opener re spelling and grammar. Makes me cringe and I have to stop myself pointing out mistakes! Brings out the snob purist in me I try to keep well buried.