Optional parameters should not be selectable from input

[Klinton90]

Is it possible to make optional characters not selectable (by mouse, crtl+A, shift+arrow, etc.) from input field?

Say my format is 99-99-99?9?9. When I enter in that field 11-11-11 then ctrl+A, copy/paste (in another place), pasted value is 11-11-11__.

[Cyclodex]

Related to #160

Changing the placeholder to space would only solve the issue visually, it still would copy all the spaces in the end. Might need some improvements.