As an example, let's look at this post. It asks, essentially, 3 questions:
- How do Bitcoin nodes know which hash to work on?
- What determines what a valid block is?
- How do I submit a valid block to the network?
The problem is that some of these questions have answers on this site, and others don't. It we mark it as a duplicate of something that answers question 3, then that still leaves the others unanswered. If we answer it, then we have information that's difficult to search for.
There's a second problem too - if I know how to answer 1 & 2, but not 3, then I might avoid answering the post altogether to avoid seeming rude.
Here's what I'm proposing: when a post asks many separate questions, edit out all but the first one. (Alternately, leave whichever seems most important.) Then, leave a comment along these lines:
I've edited your post down to one question. I did this because making posts cover fewer topics makes them easier to search for. It's OK to [re-ask](https://bitcoin.stackexchange.com/questions/ask) your other questions. You can look at the edit history to see the removed part instead of retyping it.
However, we wouldn't do that if the questions are closely related. For example, the questions, "Do I need to encrypt my wallet?" and "How do I encrypt my wallet?" are closely related: if you want to know one, you probably want to know the other. In the example question, I'd put 1 & 3 in the same post, and edit out 2.