One of the problems with hacking the hashtag (#) in the URL is that this fragment identifier is supposed to be used to identify a portion of the document. As such unexpected things can happen when you try to exploit the hash tag for other purposes.
For example, with older of versions of Microsoft Office you cannot use a pound character in a hyperlink:
Some email applications may unexpectedly strip the tag, attempting to be smart about handling it in the RFC 3986 sense (not anticipating this use-case at all). When the data appended to the # is a dependency to view the link, it can more easily render the link unusable.
For example, with older of versions of Microsoft Office you cannot use a pound character in a hyperlink:
https://support.microsoft.com/en-us/help/202261/you-cannot-u...
Some email applications may unexpectedly strip the tag, attempting to be smart about handling it in the RFC 3986 sense (not anticipating this use-case at all). When the data appended to the # is a dependency to view the link, it can more easily render the link unusable.