It’s good for email and personal sites (those aren’t dead, but they’re more popular for people that either write a lot or are self-employed). I’d only use a personal domain for self hosted apps if the users are just you and your family.
For something like hosting Lemmy, with users you don’t know, I wouldn’t use the same domain as where you host your other personal stuff, even if it’s not your name.
That’s a feature supporters of imperial thinks it has. Even if imperial/some special third option is better for guessing, the difference has to be big enough that it’s worth the hassle of having multiple systems or converting everyone again. If it’s not worth having two systems but it is worth converting everything , then you still have to keep or prove that it’s worth losing the conveniences of metric like 1 km = 1000 m , 1 L of water weighing 1 kg , water freezing and boiling at 0 and 100 °C