Hmm, idk, some parts of the code could use better adherence to a style for consistency, and it may encourage new contributors.
I feel like styles are largely based on opinion though. And in situations where a style does help, such as avoiding confusing/ambiguous expressions, NodeBB rarely suffers from these problems.
I am against tabs though. I hate them. Used to love them, but after using spaces, i can never go back. (I really really hate semicolons too.)