I am afraid that it isn’t possible to change the toggle comment characters. I didn’t find a way to do it and I see that it doesn’t work for other Xcode supported languages like python, html, and applescript either… so I am pretty sure it is not possible.
Yes I changed it to always use Safari some time ago because of a bug in MacOS 10.12.5.
I think apple fixed the bug in 10.12.6 so if you are using that or later you can change it back like this:
Type in terminal:
open -a Xcode /Users/[your user]/Library/Developer/Xcode/UserData/Behaviors/doc-lookup.cfx.applescript
Now Xcode opens a script file. In that file locate this part:
tell application "Safari" open location docUrl activate end tell
and replace + save it with this:
open location docUrl
Now the docs should open in your default browser.
Thanks, Jacob