In Excel, I can create a hyperlink to a web page. However, if the URL contains a # character, Excel always converts the hash sign to space-hyphen-space so the link no longer wor
This is not a browser problem. MS Office applications are mangling URLs with a # being replaced with ' - ' (the %20 is a space).
This annoying problem is admitted to exist by Microsoft themselves. To quote from that page:
These problems may occur when the name of file to which you create the hyperlink contains a pound sign (#).
NOTE: The pound sign is a valid character to use in a file name but is not accepted in hyperlinks in Office documents.
Their only workarounds are to remove the offending # or to copy and paste the URL from the document ... utterly ridiculous considering the reason most people would be using the # is to make it easier for users to find content.
Request that Microsoft improve this behavior by voting here: https://office365.uservoice.com/forums/264636-general/suggestions/32273917-stop-mangling-urls-containing-a-so-we-can-link-t