It is faster to type // than /* ... */ . Any time you type the same character twice it is much faster than typing two separate characters.
Further because I write a lot of JavaScript too I sometimes make the mistake of putting a // -comment into my CSS which breaks things. And when things break in CSS you usually don't get a clear error-message about it.
It is always difficult to switch between two languages. I would prefer something like JavaScript stylesheets, if that was possible.
True. But the IDE can of course help. In WebStorm I can select multiple lines of code and press Ctrl-/ to have them all turned into single-line comments if they were not, and uncomment them if they were.
Single-line comments have the benefit that it is always clear to the reader which lines are comments. Whereas if you use multi-line comments to comment a large section of code it is no longer clear when reading it whether it is indeed "inside" a comment.
And finally having both types of comments available is useful because you can multi-line-comment a section which already contains // -comments, whereas you can not multi-line comment a section which already contains multi-line comments.
This seems like the worst of both worlds. If you're going to use the /* */ I don't see why you'd bother with // unless it's about recognizing a comment in a single line.
