Cool.
It doesn't really matter when they're talking amongst people who know the language, but to people who
don't it would seem very accented and hard to understand.
Like the person from the roleplay. She basically speaks the same language, just with a few variations. If she was talking to someone who spoke her dialect, then I'd drop the accent between them.
“She'd become a governess. It was one of the few jobs a known lady could do. And she'd taken to it well. She'd sworn that if she did indeed ever find herself dancing on rooftops with chimney sweeps she'd beat herself to death with her own umbrella.”
― Hogfather