Personally I am a big fan of the Stack Overflow style routing for users:
https://stackoverflow.com/users/17174/sam-saffron
In Discourse land this would be:
https://meta.discourse.org/u/17174/sam-saffron
This kind of gives you the cake and let’s you eat it. Buy yeah I totally get the objection to “I don’t like 17174 anywhere in the URL, usernames are stable”
That said, we have survived for this long on our existing routes, its just that once every few years some edge cases pop up.