I reckon it’s probably about 50/50. There are definitely a lot of genuine posters but there are also bound to be a lot of bullshitters.
I think a lot of posters are middle class professionals living in London. They’re more likely to join MN because like pp said, they’re more likely to have moved away for university or work and so are less likely to have a big community of family, neighbours, and longstanding friends so when they need support, they post on MN.
I’ve noticed the middle classes seem more anxious in general so they’re more likely to be seeking reassurance about pregnancy symptoms, children’s health, work situations, etc.
I’m a professional but not middle class or on a “MN salary” but I’ve found it helpful over the years learning from people who are older and wiser, probably more so when I was younger.
A lot of posters have been around for years so they’re older and have had more time to progress in their careers so they’re earn more as well as being able to buy fancier houses than might be achievable today so their level of wealth can be unimaginable for someone like me.
I’m often shocked at the “will my £500,000 pension be enough for me to live on? I’ll have the full state pension too, I own my home outright and have savings of £200,000” - I wonder if those posts are just to wind people up but on the flip side, I can see that for someone who has never experienced financial hardship and has only been around people much wealthier than them, it may be a genuine concern for them.
There are plenty of wind up posts that are obvious though “I live with my husband and 10 year old son. We have a household income of £250,000 and we’re finding it difficult to manage, we live off beans on toast and I haven’t bought a new item of clothing in 20 years” - those threads are amusing, it’s more funny how many people believe it and get invested.