[duskwuff]

> I think the only character that Macs don't allow is the colon.

Colon is allowed in the filesystem; it's displayed as a forward slash in the UI.

(There's historical reasons they do this: Classic Mac OS used colon as a path separator.)

[IIsi50MHz]

And it was merely not recommended to use a fullstop at the start of a filename. Device drivers —perhaps just for storage devices — were usually named this way (and also marked invisible). There was an alleged chance the OS would try to load your non-driver file as a driver for the device it resided on. Though I was unable to make it happen.