That was my first thought as well.

Supposing this project gets off the ground, maybe even somehow surpasses linkedin, some investor will come along, flash a big pile of cash at the owner and bam, through various monetization strategies to make back that money, you end up back at linkedin.

Linkedin isn't the way it is because they didn't know how to make good UI.

As far as being doomed, you could easily be right. But couldn't the same case be made that HN would just be as bad as any other forum or comment section and therefore not worth doing?

It might. But it might make the founder rich en route to that doom.