Question threads have sort links like "?order=vote_score" that are not nofollowed, which is causing lots of duplicate crawl URL errors in Google Search Console and takes up a lot of crawl budget.
The Q&A forum type is creating some SEO issues for us as well. I recently reported the schema markup here, and now I just discovered that the "?order=vote_score" is causing duplicate content. I hope the dev team can look into this and help fix these issues.
@Anatoliy Not at all. Technically speaking, that would be the alternative, but seen too many times that things still get indexed by Google even when I put a rule in the robots.txt. The ultimate solution is nofollow.
It's worth mentioning that this wouldn't be true. There is a rel=canonical tag present that doesn't include filters and that is how you prevent the same content from being indexed with multiple URLs.
Crawl budget would be a separate issue (though there isn't strictly a guarantee that nofollow blocks a search engine from actually following a link.
@Mike Thanks. You are correct on that. Sorry I didn't update my old comment. I saw that Google has decided to ignore those links due to the dedicated rel=canonical tag.