If you mean to select text as for coping it, everything is the same, only selected. No given reason is shown, - (minus sign) stays the same as when it's not selected.
EDIT: I enabled guests to see thread closing reason, so you could check for yourself:
http://slobodni.net/t116947/
Guests obviously don't see minus sign and x to delete reason, but also don't see reason at all, just user name of person who gave reason.