I don’t think the lemmy.ml admins have been coy about it.
If you go to the lemmy.ml home page, at the bottom of the right column is a list of admins.
The first admin’s profile banner is a picture of Mao. And the second’s profile pic is a photo of Fidel Castro. The other two don’t have profile pics that are explicitly authoritarian communist and I haven’t had the patience to look through a whole lot of their posts or anything.
Just a couple of Reddit threads (via libreddit.hu) on the topic: one and two. Unfortunately what they link do doesn’t appear to be in the wayback machine as far as I’ve been able to tell.
It depends on your specific case, of course. That 0.4mm is indeed a good rule of thumb. But also, assuming you’re dealing with FFF-printed parts, generally if the two parts slide together along the layer lines, it’ll feel just a little looser than if they slide together perpendicular to layer lines. That’s just due to the ribbed texture inherent to FFF printing. Though printing at smaller layer heights will reduce that effect and also make the parts fit just a little looser over all.
Aside from that, probably the best advice I can give is: