Do not end a file or directory name with a space or a period. Although the underlying file system may support such names, the Windows shell and user interface does not. However, it is acceptable to specify a period as the first character of a name. For example, “.temp”.
I suppose Syncthing just follows these naming conventions for Windows machines for certainty’s sake.
Android has many limitations as well due to using VFAT on its internal storage, so be careful, because if you use any of characters like " * / : < > ? \ | in your filenames on Linux, they won’t sync to Android too .