The skepticism is not because most health experts believe reinfection is unlikely (OR the opposite). It's because the virus is so new they actually don't have good data on reinfection rates yet. Immunity is a resistance that fades with time. With some things like Chicken Pox immunity lasts many decades. With others it can be as short as months or weeks. We don't know that duration yet for COVID, so healthcare professionals are telling us it's irresponsible to build plans around it. I'd have to agree.
On the original thread, "herd immunity" strategies don't come from "let everyone get sick and those who live will give us herd immunity." That's insane - just for COVID it risks 1M-2M US citizens that would likely die if we didn't act. You wouldn't go grab samples of Ebola or Smallpox and inject everyone with it - you do everything you can to prevent their transmission.
The whole point of a vaccine is to give a population herd immunity WITHOUT the risk. Think about polio. Do we give everyone polio and then say "welp, those that didn't make it, thanks for your sacrifice! we're all immune now!" Of course not - how many people do you know in an iron lung? That was a real thing, not a conspiracy. To eradicate polio, you make a vaccine and inoculate the population. A vaccine gives the same or better herd immunity as actual infection, but without a bunch of people getting sick/dying for the same result. In fact, this vaccine is particularly safe because it's an mRNA type, which gives your immune system protection codes without having to inject the virus itself.
For those on the fence, just consider this one thing. If your rationale for skipping the vaccine is "I'm strong, I don't need it" you aren't impressing anyone. There aren't any songs sung or books written about "that guy who beat polio without the vaccine". If it makes you feel better about yourself, great, but to everyone else you look foolish, not smart. You're proving a point, but not the one you think.