MN phrases/words I hate ... NAICE instead of nice sets my nerves on edge. Who the fook says that in real life?! 
And 'picky bits.' shudder...
'Can I get a latte?' is annoying, but I have to admit that I do that myself sometimes. 
'I always batch cook' gives me the rage. I cannot say why!
And I have never heard of a 'pop of colour' ... But I have heard of popping somewhere. Doesn't bother me really, as 'pop' does mean to go somewhere for a short time.
One thing that REEEEEEEEEALLY pisses me off though is not a mumsnet thing; it's a weird 2010's thing ... This newfangled way of saying something new coming out has 'just DROPPED!' 
'The new Taylor swift album just DROPPED.'
'The new trailer for Once Upon A Time In Hollywood just DROPPED.'
'The new single by Ed Sheeran drops on Monday.'
What.
The.
Actual.
FUCK?
What happened to saying the new album/film trailer/single is RELEASED?!
Dropped doesn't even make a remote fraction of grammatical sense
From Google...
dropped
adjective
1.
having fallen or been allowed to fall vertically.
"I have been trying to keep this area free of dropped apples"
2.
made low or lower than is usual.
"organza dresses with dropped waists"
3.
to let someone go/free yourself from them.
I dropped Maria as a friend as she kept letting me down.
Where in the name of SHIT did the idea come from to use the word DROPPED/DROPS for a new single/book/album/film trailer being released? 
Gives me the rage! 