It's suitable for packet writing on optical media (both re-writable and write-once!) that require wear-levelling because it is, in essence, a log structured file system which means that the file system is one big journal (which makes it similar to logfs, lfs, nilfs and jffs2, though I probably wouldn't put it on bare flash).

That doesn't mean it's unsuitable for other uses, and I know of no reason not to use it on a hard drive or a flash drive with a flash translation layer. It should be a better choice than VFAT, and I've heard it being cited as better choice than NTFS (which when you have to use NTFS-3G must be true). And it's the only other filesystem that works on all modern operating systems out of the box. Which is why I inquired about any known issues here.

Apparently I stumbled on an unexpected kind of issue though: It's hugely unpopular except for optical media, and nobody is using rewritable optical media any more, so I apparently I stumbled on a rare bug that nobody ever noticed, and there are probably more to come.

That's unfortunate, since from the little research I did, UDF promised to be the best filesystem for any kind of removable storage.