Is it permissible for a husband and wife to flirt with each other in public under the pretext of personal freedom, and is there any religious text that supports this?

It is permissible for spouses to address each other with flirtatious expressions, even in front of people, as long as the speech is not obscene or does not lead to corruption. The prevailing customs and traditions should be observed; if uttering such expressions is considered immodest in the view of some, then it must be avoided. For modesty is among the best of manners.