I use it for emphasis. Say for example, I thought someone's post was funny, I would use 'nnn'
For me there are levels of emphasis:
nnn - I find it funny
ddd - I find it super funny
dsdsaf;a - I'm actually cackling so hard inside to the point I can't type a proper post
In cases where I use it as part of my post for example, 'nnn not when she looks like that' it's more of a restrained giggle. So like, I find it funny but I'm trying not to laugh sort of thing
As for kii, it's like lol/ ha but I guess more versatile.
