Reading the comments here makes me overly conscious about choosing my word carefully. Say “cure” instead of “medication” and there goes the point you wanted to make!
Lemmy is reddit 3.0. Early on, Reddit was basically only a website for tech nerds and misfits; atheism and jailbait were some of the most visited subreddits, idpol and divpol weren't a make-or-break-your-family issue back then but there were still a ton of terminally online furries (yes if you're a furry you're weird, but weird is fine, let that freak flag fly.) I'm including myself in the group of outcasts and misfits, and my freak flag flies in weird ways too. I've been on Reddit since the default UI was , although it hadn't changed much over the years before the redesign. Notice the quality of submissions though - it was a place for the intellectually curious.
But you have a large subset of users who use pedantry and grammar nazi`ism as a way to feel powerful when they're powerless. It's like picking on those lower than you, when you're in the bottom of the pecking order.
Those people saw reddit go from their bastion of freedom to the corporate ad-haven it is today and all came here. You also have a lot of younger people with the time to kill and are just trying something new.