Especially in the JS space[1], there are lots of historic answers upvoted on SO that are now wrong and you have to scroll around (or find a slightly rephrasing of the same question that occurred more recently) to find a good answer. Unfortunately the longer a question is around both the more answers it has and the more likely the answers are to be wrong. On forums / mailing lists the question would just be reasked. On SO it is supposedly a wiki so new versions of the same question gets closed.
[1] Because it has evolved a lot, Rust has similar issues, as I'm sure lots of languages do
I really do try my hardest to keep old questions and answers relevant. Stack Overflow allows editing Q&A for a reason, and any time I stumble on an older post, I at least think about updating it.
One thing that I've occasionally found frustrating is that someone sees a question was asked 2 years ago and thus assumes that it must be invalid / out-of-date. They simply don't look at the edit dates.
Remember that Rust has a pretty strong backwards compatibility guarantee. Any answer using only the standard library in the last 3 years should still be valid (crates are a different concern). If you find a question you think has become stale, add a bounty to it to raise attention — that's the SO recommended path of action.
We also have a Rust chatroom on SO where a bunch of regulars hang out and people are welcome to pop in and ask if a Q&A is still valid.
I have nearly given up looking for JS answers in SO because they are such garbage these days. I am learning Rust right now and still find answers on there useful.
We actually have a specific tag for those cases (`rust-obsolete`), so if the question / answer cannot be rehabilitated for Rust 1.0, that's a useful thing (I also try to add an in-question disclaimer to make it easier to spot)
A lot of the editing I do is to improve the grammar, reduce fluff, use Rust-standard indentation, improve the formatting, include complete error messages, update links, etc. None of that should affect users of older versions other than to make it easier to get to the core content of the Q/A.
When a new Rust feature comes out, usually the original part of the answer gets a header denoting the compatibility. https://stackoverflow.com/a/28953618/155423 is such an example.
Note that SO does keep a revision log of edits (e.g. https://stackoverflow.com/posts/28953618/revisions) to a post. You can browse that if you think there might be something hidden that's worth exploring. This doesn't necessarily help with search engines, of course.
And how many of those slight rephrasings never got a chance to get a more relevant, correct, modern answer because they were marked as a duplicate?
- they get marked as duplicates, so that all future people coming in via Google get funnelled to one place
- that place gets new modern, more relevant answers
- they get voted up because they're useful
- people add comments about answer compatibility
- they either overtake the other answers and the other answers stay around as history, or if they don't there is a single place where relevant answers can be found.
1 question with 10 answers is a lot more discoverable than 10 questions with 10 answers.
One leads to 9 answers to skim-read and ignore and 1 answer to use.
The other leads to you finding 6 questions and 6 answers you don't like and 0 answers to use and missing 4 you didn't know existed.
Sometimes you have to work out the underlying Q is and answer that even if the OP doesn't want to hear it.
And often times you have people trying to "work out the underlying Q" leaving your question still open but with useless answers.
About that, there seems to be a recent trend that answer quality is so low that the only actual useful information is on the comments.