For
It improves communication and teamwork.
Against
It may exclude or disadvantage non-native speakers.
Anonymous excerpts, translated where noted.
“Speaking in a language everyone knows also enables others to chime in or comment.”
“There is a genuine benefit to coworkers being able to overhear and understand each other.”
“I feel like this is very discriminatory, especially since some of our employees communicate better about the work they're doing in their own language.”
“I believe it shouldn't be a problem when I'm sitting at my desk minding my own business.”