if theyre my friend, sometimes they make it obvious through the way they speak to me. if not, it's usually much harder to tell, unless they make it blindingly obvious such as posting the same question in a million different ways.
yes because they will sometimes ask the question un anonymous and then ask it later as anonymous but attempt to change up the way they ask the question.. i can also spot out the ones that use the " its not its my friend" type of questions...
I never pay attention and don't care who they are. Half the time I don't look who's posting even when they aren't anon. A fair amount of the time I don't even notice if they are male or female. I just read what they have to say.
There have been a few times I was able to tell because they had messaged me before and I had talked with them and gotten to know them well enough. But I don't exactly dwell on what other users post here, so most of the time I can't.