What's worse - and this is an old problem - many results are for irrelevant variations like displaytype=print or showing the edit history

It's a pity we can't control the bots better.

FWIW: here an old workaround I'm using for Google (already for at least 10-15 years):

https://www.google.com/search?sitesearch=www.perlmonks.org&q=%22Node%20Type:%20perlquestion%22%20inurl:node_id%20-displaytype%20-index.pl

NB: by design it will only find complete threads.