I have a daughter. She isn't 'dearest daughter' or even 'dd'. I have a husband. He isn't 'dearest husband' or 'dh' (he is sometimes 'twattish husband', though).
I find the use of acronyms to be a terrible barrier to communication in general and on this forum in particular.
So is it laziness on the poster's behalf? A desire to bond by using similar 'speech' patterns? Is it simply quicker? Or am I being an unreasonable old trout?