Yes- Staves off boredom and allows you to experiment or experience multiple aspects of the mud simultaneously.

No- Promotes fair weather play. This can be detrimental to your main if you start to enjoy the alt more.

My old mud had a one character limit. It was SWR, and force sensitivity was something you could find automatically only after 20 hrs played. It was necessary there to prevent people from rerolling constantly to get a jedi. It also made you invest a certain amount time into your character and made you more invested overall as you were playing a concept that wasn’t meant to have force (really rare) so if you didn’t get it you hadn’t lost out. Here, that’s not an issue at all, though there are pros and cons both ways.