It also heavily depends on the player behind that other character, and on the "personality" of your character in question. Some characters are easier to "change" than others. And sometimes it may be impossible to change facets of your character at all, because of OOC reasons - i.e. if you think you would no longer enjoy playing a certain character. It can be hard to get out of specific, deadlocked situations, so I can understand that not everyone wants to play through these, really.The "low" amount of players may make people seek RP opportunities wherever they arise as there might not be many good opportunities even if the "right" course of action would be just to exchange a few pleasantries or rude remarks and be off with your daily business.
A good Crusader does probably not want to fall from grace and goodness, become corrupted and then end up as a force for the evil side at all. (Especially not if the evil side is very small and you'd almost feel as if you are playing alone and isolated. I really think the most powerful feature a guild can have is 'tele', or put differently having a 'community feeling' within that guild. As in having likeminded people around.)
Two extreme examples for sudden personality changes which may be very difficult:
- A jovial, happy character type does not necessarily want to jump to the other extreme within a second, suddenly starting to torture enemies. Even if there may be a reason to do this, like extreme revenge, devotedness or whatever, but this seems really hard to pull off.
- Vice versa the angry, almost naked cannibal might feel quite uneasy when he, all of a sudden, has to appear dressed in fine clothes and change his diet. (You can see how much switching from meat-eater to vegetarian in real life can affect, and back again. You'll go through a local mall and realize that you suddenly have less options available compared to those without such a restriction. Not saying this is good, or bad, it's just ... different)
But it also should be possible to "change" or otherwise affect the personalities of characters - even of those being older and more established. Otherwise you would have somewhat stale and boring characters populating a MUD. In my opinion it would get dull to become "more powerful" just for the sake of .. being more powerful alone. The "power" or strength of a character alone should really play only a very, very small role. Why not have weak Sathos or weak Crusaders if they are great at roleplaying for instance? Sure you may prefer to have only strong chars, but that means to leave out weaker ones, plus as a few others said already - often the option to play is better than not being able to play at all.
(On a belated note, this is also why I believe there are quite few halfling characters, especially VERY few "famous" halflings. Sure, roleplaying a halfling is fun. And ideas such as areas only accessible for very small characters are GREAT to have. I also guess halflings would really be perfect rangers/scouts/thieves, but from my perception other races are a lot stronger. Halfling thieves may be a small exception, but I have no idea if they still exist. But what about active halfling rangers, crusaders, clerics, scribes? I really think it boils down that halflings are a bit left out here in the overall picture, in part because the combat system prefers those who can dish out damage and soak hits. I am not complaining or suggesting to adjust the combat system at all, I just think it would be nice if there be more niceties for halfling characters to "stick around" for longer. But enough of that.)
Back to changing personalities of older characters. I am not stating it should be easy. However, it should not be impossible either.
Other playercharacters - or sometimes their absence - will always have an impact on the development of a character. As will certain unique events, like slaying a dragon, destroying a guild, and so forth.
These factors all heavily influence other playercharacters already.
Last but not least, I would like to finish saying that the underlying code has a huge impact here. Players often happily try out new commands/stuff and this often triggers action/reaction, and so forth, to name just one example.
There was a little bit more I wanted to write, but my note is again way too long, so that's it.