- and _ tend to break text selection.
That said, iOS and Android text selection have gotten worse recently, IMO.
As a developer I will be exposed to ids being displayed in code, terminals, browsers of various sorts, database editors, json dumps, text editors, api responses, chat messages, you name it.
The _ and - symbols make this difficult in the edge cases of all of the above. Do you call it dash, or underscore? Line? Hyphen? Binder-strich?
&etc.
I would have gone with adding the @ and ~ symbols, those are at least parsable in human form as well .. ".. email symbol and squiggly thing .. "