Block comments deletes lines instead of adding them (at least in c)

[homogulosus]

Hi, I am using neovim 0.5.0-21453e8 on macOS X 10.15.6
When commenting in block the behaviour is to delete two lines after the box which is a big inconvenience. The expected behaviour should be to add these lines to prevent losing work already done. I can imagine this is a big problem if the user does not notice this happening.

Again, great work. If we can solve this issues I am totally switching to caw from vim-commentary