Comment by Jenda_

I don't use spaces, because I want to be able to run ad-hoc shell one-liners when working with my data without worrying about quotation and similar stuff.

I also don't use :, as I have ran into problems with both Bash and its completion and FAT FS. Unfortunately, I routinely have timestamps in filenames, so I need to use +%F-%H-%M-%S instead of simple +%F-%T.

One thing has improved, though: I have not run into problems with ěščřžýáíé (which my language is full of) for maybe a decade, except on OpenWRT where space seems to be scarce to support non-ascii.

Edit: I now remember one problem, getting images for a website from an OS X user, which used combining characters instead of direct code points (https://en.wikipedia.org/wiki/Unicode_equivalence#Example), but HTTP requests got normalized in some browsers, leading to strange 404s.