I think this was done a while back. Frame builder used heated to free the seat post which toasted the original paint. It was up for sale a about 18 months ago in it's unrestored state. Metal work was fine.
I shouldn’t really get upset by ignorant experts but I do so thanks for those established members on here that have vouched for me.
Is it ugly? Yes. Have I been honest about it’s condition? Yes? Is it rusty inside? Who knows? It’s a 30 year old steel mtb so it’s as likely with that one as any other I supppse. Is it overpriced? Maybe. But consider this. If you buy it and spend £200 on paint and decals (to your choice of course, that is the beauty of ratty paint) are you going to loose money on it? I doubt it.
I’ve got £435 invested in the frame so I’m just trying to get my money back. When I listed it here before with images showing the paint burnt off there were all kinds of bonkers questions about whether the hear had damaged the seat tube? Well, just check the burning point of paint vs steel and you get your answer.
So I invested a couple of hours in rubbing the burnt paint off and re-spraying the area. It looks a lot better now. I’m not asking any more money for it and at least you could ride it like this whilst you chose your paint scheme and waited in line for the Argos paint team.
I don’t mean to sound (too) defensive but maybe consider whether the advert you are referring to might actually be genuine or not.