It's not the vocal part that puts people off. It's the fact that every time Jonsu opens her mouth, out come insults, scorn, anger, sexually oriented comments, and various vitriolic comments. Up until she got booted from the elders, Jonsu literally showed no knowledge of the stars, no decorum, no civility... nothing but personal attacks against everyone.
Now you're getting your timelines twisted. There was a very distinct period where Jonsu stopped exercising decorum and civility with the Elders, and it coincided with the day Medugnatos was made Light. The vitriol, insults, scorn, etc was purely a result of this, because she didn't have to care anymore. Prior to that, I'll agree she wasn't the easiest person to get along with, mostly because she wasn't afraid to call people on their bull!@#$, and when you have a group of elders who are notorious for flip flopping on issues when its convenient, those calls are going to get made.