I've used reddit.com before but I never made many posts or comments and I haven't used it in years. I'm pretty sure there was a period where I visited it regularly though.
I don't think I've ever posted anything with facebook.com or twitter.com either. I never browsed them for fun, and if I want to coordinate with someone in my family I just contact them directly. I do use youtube.com a lot though.
I tried using pleroma but I haven't used that in a while either. I prefer lemmy much more (probably because posts being different from comments provides more structure).
I think this is not among the most important things to be talking about.
https://www.hsph.harvard.edu/magazine/magazine_article/fluoridated-drinking-water/
https://nutritionsource.hsph.harvard.edu/fluoride/
https://duckduckgo.com/?t=ftsa&q=fluoride+site%3A.edu&ia=web