I guess it just depends on the beardie's personality. We have 5 beardies, 4 are rescues. When they were little, especially our two babies (who are now 1 1/2 yrs old) they were together in one tank. But my husband is retired, so he kept an eye on them. When they were 4 mo old, they were put in different tanks. I always thought the 3 females would get along, but they can't stand each other. We give them each time to roam our living room, which is completely beardie proofed. One day I decided to see how Angel, Sweetie and Issy would manage out together. Sweetie, who's the oldest at 3 yrs old, tongue pushed the other two. Issy, our youngest, ran at Angel with her beard puffed out and her mouth wide open, trying to bite her. Angel had the same reaction. So that was the end of that!
We also have two males, Lonzo is 6 yrs old and Rubio is 1 1/2 yrs old. Lonzo was having trouble being out of his tank, he didn't eat for 2 mo, he was just so turned on by the three girls. So Lonzo has his own room (our office) and never sees the other 4. Rubio enjoys bobbing &
black bearding the girls and it doesn't affect his appetite. Even so, his tank is in the dining room & the three girls tanks are side by side along the living room wall, so when they're all in their tanks they can't see each other. It's all normal beardie behaviour, I just didn't want to take any chance that they'd hurt each other. I also won't allow them to breed, we don't have the $ or the space to take care of babies.
You're right, everyone has their own opinion. I've just seem some really nasty bites, and sometimes it's babies biting babies. Issy only has 1/2 a tail because she was attacked by another baby while at a pet shop, we got her out of there the minute I laid eyes on her. Rubio was also attacked as a baby, he's missing most of the digits on his right front & back paws. It hasn't stopped him from eating, but he sure was tiny when I found him at the bottom of his tank at the same pet shop. So that's how we got our two babies. They're both fine now, but had to be nursed alot when we first got them. Rubio is now 22" long and 750g; Issy, without her full tail, is 14" long & 418grams. So having them in separate tanks worked for us. Depends on the situation.