I'll dare to add an opinion - some light hearted banter seems OK with me and I do it but flirting may cross a problematic line. A compliment to one person may be an insult to another after all.

My general strategy is to use self-depricating humor - something along the line of "you're probably about to get a laugh at my expense but do I have any chance of getting on the upgrade stand-by list" or alike. My 'respect' barriers are just too strong to make any comments about the person's looks and/or attire.