one person, two phones, one text thread
Yes. iMessage allows this with the following caveat.


Joe uses iPhone A to sign into iCloud with his account. The phone number for the first phone gets associated with the AppleID / iCloud account.
Joe uses iPhone B to sign into iCloud with the same account. Now both phone numbers are associated with the same Apple ID.


Now - set the "caller ID" in iMessage from both phones to be the same number (either can be chosen) and for iMessage recipients - all new messages started from iPhone A and iPhone B will be "from" one number.

This doesn't work for SMS since the carrier assigns the "correct" sender in that case.