There is a behaviour of Obsidian.md which I think may be unintended.
I use a smaller font size, by reducing (cmd + “-”) the text size.
Obsidian.md remembers this choice when I reopen.
However, the moment I click “open another vault” and the prompt reappears, this new Obsidian.md prompt forces a reset of the smaller font size.
I am using 2 vaults, so this becomes a little bit annoying if I close one vault and need to reopen it, the text resizes to 100% all the time.
(Otherwise I have no other thing but praise for the developers of Obsidian!).