(I use quotation marks to denote that the note is dedicated to an article on the web - it makes the difference clear in e.g. graph view)
Operating system: Android 11, MacOS Catalina
There were a few threads that reported this bug, but they were marked as fixed. The only remaining discussions are specific to creating notes on mobile, not creating the note on desktop then attempting to sync it to mobile.
The only thing people often forget: Like with Linux, it depends on the filesystem used! On Android, the internal storage usually uses ext4 (on which all the above works without any problems). Users often format their SD cards (external storage) using the FAT32 filesystem, which doesn’t allow characters like above.
So if you format your SD card using ext4, you’ll have no problems. Except that you can’t (easily) access them in a card reader on Windows.
Alternatively, if your synced vault isn’t too large, you can store it on the internal storage.
Don’t know if Obsidian Sync supports this correctly, but it should. (Syncthing does.)
Otherwise @WhiteNoise is correct, of course: Know your OS and your filesystem types, and avoid things that might be incompatible when mixing.
No, this is not an issue of internal or external. Android has restriction on top of the filesystem used and we have (and the api we use) to honor them. Syncthing uses a lower level api and it doesn’t respect the Android spec. This is their decision.
Gotcha, I didn’t know Android had these restrictions. Might be helpful to let users of Sync know when they are creating a note containing characters that won’t work on all OSes. I’ll remove the invalid characters from my note names.