There's no rule against a specific Pokemon being put on the AH
multiple times. There's a limit to how many auctions you can have
up though, to keep spam in general down.
to be aesthetic or not to be aesthetic
that is not a question because I am not aesthetic at all and nor is
this signature
I occassionally do this, for example when I am shiny hunting, I
would put the hatched non-shinies in the auction house for like 9
PD (depending on the Pokemon), because otherwise I would just be
releasing them. By putting them in the AH I can still get some PD
from them, as other players might need these Pokemon for their
Pokedex