I am seeing more and more people at my work using private chat groups on MS Teams which is good that Teams is getting more usage. Private channels are not inclusive for others, which I think is a bit of an issue. I understand the idea of private channels it is a bit akin to email more focus to a group and safety. Just like email, private chats lock the conversation and ideas to a group in the know, not the boarder team.
On the other hand, Public channels open up that communication yes yet make is harder to chat openly as you know every body can see it. Plus with a public group there can added noise from others which for sure will distract the core team.
Trouble is it hard to figure out the happy middle ground where you have a public group to chat and brain-storm ideas and have a private core group/team chat to more focused details of the project.
There is no right answer, unless you said all chat should public and the people understand when and how to interact. Even than it will never “always” be right.
“In the long history of humankind, those who learned to collaborate and improvise most effectively have prevailed.” – Charles Darwin