RegEx literals like /^\w+:\/\// render as ending with a comment, even though the second to last slash is escaped.
AFAICT, this doesn't interfere with the actual running of the script.
Compare to the visually correctly indicated highlighting in VS Code, for example:
Is there something that can be done about this, or is the script editor a boxed-up component by Microsoft?
The editor’s syntax highlighting rules aren’t advanced enough to handle all of JScript’s syntax, with regex in particular. Not sure there is a short-term solution.