Before I continue - this discussion seems to be offtopic, so if you think that we should move to another thread, then maybe it's a good idea. But I think we can continue here, because original topic seems to be finished - OP has his answer. You decide.
Secondly - I would like to continue, because I see an opportunity to learn something new. So I will try to give you some arguments, and I'm open for counterargument.
Franz I like this kind of discussions, where we can use numbers. I did some calculations for this particular discussion page.
It turns out, that you are right - there is 210,14 KB of JS (but actually no megabytes) to be downloaded (after compression) plus 13,88KB of HTML, plus marginally 678B of JSON to be downloaded, after scrolling for more posts.
I saved this whole page as HTML document, and it is 144,5 KB big, so it is smaller. And probably would go down to about 40KB after compression. I don't count CSS files, and images, because it has to be downloaded anyway.
But - most of JS is the same for all requests, so it has to be downloaded only once, and then it is cached. If I have cache turned on in my browser, then JS file's size goes down to 26,8KB, and this is smaller than downloading whole page every time. And from there one, if I load another thread I just have to download JSON data that is usually less than 1KB.
I would be happy to see some comparison for energy consumption, but I have a feeling, that it would be marginal for page like Flarum.
As I already mentioned, privacy is not the reason for not using JS, because one can do many other thing to avoid being tracked, and at the same time use advantages of JS.
The only real reason to turn it off that I know, is to avoid malicious JS, like cryptocurrency mines on ads, or exploits of Meltdown/Spectre holes.
So Richard Stallman is NOT against JS in general, but only non free ones. But Flarum is free software, both as in freedom, and as free beer. With proper marking in Flarum's JS code LibreJS would not block it, because it's free (as in freedom). Actually, maybe it's a good idea to add this marking, as described here?
Concluding - I think that there is no reason to block JS by default on every page, especially when you can trust it. That is the case of Flarum, because it's free. JS gives web much more opportunities in functionality, and saves bandwidth, so it's worth to be used.
As I already wrote, I'm open for counterarguments, to maybe learn something new (as I already did by reading about LibreJS and free JS).