A couple of things occur to me
1) sometimes a trivial "problem" may be a person's "dry run" at posting something more serious
2) loneliness may prompt a person to post even if they haven't got a real issue to post about, just to start up a conversation
3) some people DO obsess about the slightest thing, this is not unique to teenagers! Open pores on their noses, ears going red, next door's old git in his string vest, the price of bread. Ageing can make us pernickety/grumpy (present company excepted) just earwig on some people's conversations on a bus or train
4) what may seem "Doh!"to you and me, may not be be so to another
I heartily sympathise though. Sometimes I do wonder how some people have reached the age of discretion and can appear so clueless, but hey, it takes all sorts.
When your own life is treating you unkindly such nonsense can be incredibly irritating, but chins up!!
And don't you dare think of leaving!!!