When one tries to trump your compliment by stating they are sexy then the complimentee claims the complimenter is sexier. The original complimenter offers that the original complimentee is even sexier by stating they are sexiestest. It would be best if the original complimenter was just thanked for their compliment of being sexy.
Me: Night :) Sexy ;)
Them: Night sexier
The next day
Me: Good morning sexiest. :)
Them: Thank you sexiestest, It's just what I need to help me wake up.