I have a custom syntax that I created to do various scope highlighting for text/log files. If any selected text or the carat is within text of the base scope, both the ctrl+shift+/
and Toggle Block Comment
via the command palette work to enter the snippet to toggle the block comment for the text/around the carat.
However, if any of the selected text is inside another of the scopes in my syntax, whether I use the shortcut or command palette, the block comment simply does the same thing as the regular comment instead of doing a block comment.