No problem with having two ,
SO LONG AS
--- they are never housed together (unless you are letting a male and female mate for a very brief period), as said , they are territorial and one will wind up dominating the other and the other will be under constant stress and will not thrive like the dominant dragon will, this domination can become physical and very violent too.
--- two who have a large difference in size should never meet each other - the smaller one will likely become a snack.
--- they are never fed together
--- they are never allowed out together (though 2 girls might behave themselves ... maybe ????) , two boys out together is asking for trouble and is likely to result in blood being shed or worse.
If you have two (espec a boy and girl) you'll see some interesting interactions when they see each other. Though two girls will arm wave and headbob at each other too.
I have three pet beardies, they all have individual tanks, and all get individual floor time each day(sometimes with one of my pet two bluetongue skinks as a floor buddy, Rex and the BTs get on well and I've never seen even a hint of aggression between the two similar sizes species).
Floor time is always strictly supervised for all my pet lizards.