This surprises me because it's a major problem for me, particularly for GitHub. I end up doing this for clones that don't even link back to the orginal:

1. Search for something 2. See the cloned issue but no results for the original 3. Copy some unique-looking text from the clone 4. Search the repo directly for that text

It's awful. Seems to be a very recent problem? Maybe the last few months?

It might be a function of your programming niche, but is it possible that you just didn't realize you were looking at a clone? These sites are everywhere.

It's a portion of the content that's cloned: the question and subsequent answers or discussion. The styling is usually totally different, even the page structure is different, to the point that I don't realize I'm looking at a clone unless I recognize the copy from a specific github or stackoverflow page that I had looked at previously in my search session.