Building your first house was a big achievement in the early days, as money took real time and effort to accumulate; much later, the challenge was finding an empty plot rather than affording a house.
Walking through players used something like stamina iirc, so you couldn't just wade through a dense crowd without some forced pauses. And once player population swelled, the bank could be just stuffed full of people just outside, in the doorway, and just inside the bank.
So what you did was carry a couple of empty barrels and water. Drop the barrels side by side in the 2-wide doorway, and quickly fill them with water. They were immovable full barriers once full. But with so many players already piled up in that area, you really couldn't see the obstacles. I believe players already on a barrel tile could move off, but there was no passing through a full barrel.
Within seconds, crowds would be denser on both sides of the (invisibly) blocked doorway, with people shouting MOVE at each other. This shouting was somewhat normal due to that stamina penalty you'd naturally hit in that situation even without a barrel. The barrel just meant you were NOT going through, but you didn't know why. It was a bit griefy, but it was really funny. And when you're an early 20s punk, it's a lot of fun.
There was a time before you could press a key to show names of anyone around. I don't recall how you saw their name, but it wasn't as easy before. When bored, I would stand in dense forest a short distance from a moongate on an island where the land between the gate and the small town was just all jungle. Anyone arriving would immediately head into the forest toward the town. But with my forest green dyed robe, dark hair, and dark skin, they wouldn't see me. One or two spells, and they were dead. Very gangky, but 20s punk fun. Eventually tab or shift was made to highlight all names visible on your screen, so that mini-game was over.
In a similar vein, there was a quiet path between a couple of towns with a little S turn, and a couple of rocks and trees at that turn. Drop one or two gold coins on the path, stand "in" the tree, and use the hide skill. You were visible if someone got close, but very faintly. Same dark green or brown robe. Picking up an individual coin usually took a few clicks to find the hit zone, so it meant anyone wanting the coins would be stationary for a moment. Murder.
And that brings us to corpse mutilation and the eventual reputation system that was added. PvP was the norm, and apparently not everyone enjoyed it. Also, ganking was the norm (not just me!). So murdering had some reputation consequences, but mutilating a corpse and leaving bloody bits scattered around was an even bigger rep hit. IIRC, too low rep and you would be attacked on sight by guards; so that meant no town visits until you had repaired your rep. Good to have a house and friends, (and alts? don't recall); then you were kept supplied and your booty fenced.
Finally, one of the first Christmas holidays of UO (maybe the first?)... there were holiday servers, all snowy and festively decorated. You had to create a new character, and you could start with your choice of a few stats at 70%. And you had random red/green chainmail. And there were no town guards. So it was a fragfest, and it was hugely fun.
Eventually typical human misbehaviors became a bigger and bigger problem, with item duping ruining economies (there was a time when you could gather resources, craft items, and actually sell them to other players who had a genuine desire for your product!), other exploits, gang-style ganking, and the usual problem of reaching essentially max skill development of characters and becoming bored (probably the cause of many of the previous bad behaviors).
Still, in the history of MMORPGs, UO was really a special thing for its time.
- edit bonus - For some time, pickpocketing actually took items out of other players' bags. So a thief with good hide and pickpocket skills could do well stealing from players. And perhaps because of the bank crowding problems (where the bank tellers were originally inside at counters), banks were improved so you could do banking just by standing close outside the bank building. That meant lines of people just standing around waiting to be harvested. Inventories were not fixed slots, so backpack and corresponding items (including bags in bags) were a real chore to fish around in, especially under time pressure. That was part of the thrill. And of course if you got caught (failed the pp roll?), you would have an immediate big guard problem. So you made sure you traveled minimally, and death just meant losing whatever you had just stolen.