I wouldn't say something online that I wouldn't say in real life.
I wouldn't give unsolicited advice either, so if I'm asked for opinion, then I'm honest. And that's easier if delivered directly. If I ask for an opinion, I also value honesty.
I've posted on here about problems in the past. I ignore the people who are obviously just being twats, haven't read the post properly or are clearly projecting etc. I value the directness of some people and find the "you sound lovely" responses grating. You don't know me. How can you possibly know if I'm 'lovely' or not?
In reality, it can just be helpful to share a situation and see a range of responses. Some of which will give a perspective you haven't considered which can be helpful. It's pretty clear which are the genuine responses.
Support can come in many guises. The least useful of which is 'niceness' and telling someone they're right when they're clearly not, which also happens a lot on here.
The only reason that MN gets a lambasted in this respect is because of the number of women who just think other women should be 'nice' at all times.