Why does Google Chrome's "Copy link to highlight" feature not work on Reddit sites?
Go to
chrome://flags/#shared-highlighting-use-blocklist
and set it to Disabled.
This will fix the problem, as long as the Chrome developers do not decide
to remove this option.
This setting is described as:
Uses a blocklist to disable Shared Highlighting link generation on certain sites where personalized or dynamic content or other technical restrictions make it unlikely that a URL can be generated and actually work when shared. – Mac, Windows, Linux, Chrome OS, Android