Could we describe what we think two questions have in common, when claiming that one question is possiblely a duplicate of another?

Question

I know that when someone claims that a question is a duplicate there is an option to edit the question to make it more clear how it's different from the other question. Sometimes it can be clear how to edit a question to show that it isn't a duplicate, but other times, even if I might feel that my question isn't a duplicate, it might not be clear how to edit it to make it more clear to others that it isn't a duplicate.

I think if the similarities between two questions are pointed out, then it could make it easier to tell what edits should be made to a question, in order to make it more distinct from what it's claimed to be a possible duplicate of. This is the reason that I think we should try to mention what a question has in common with another question when linking a possible duplicate.

Answer 1

This is already possible, and I see many people actually doing this: they edit the automatically generated "Does this answer your question? [Link to original question]" (formerly: "Possible duplicate") and add information like "In particular, look at [user X's answer]" or perhaps "That's a different error message, but the solution is the same.". Just like with downvotes and comments, there's no point in making such an action obligatory; most of the times, the duplicateness is quite obvious.

Answer 2

^{Note: I'm interpreting this post as a suggestion that it would generally be good etiquette for duplicate voters to include an explanation, rather than a feature request to make it possible (which it already is)}

There's no need for duplicate voters to include an explanation by default. An explanation is almost always unnecessary. It's usually obvious why a question is being suggested as a duplicate, even if that duplicate is incorrect.

For the cases when it's not clear, the duplicate suggester is pingable just like any commenter, and can easily explain themselves if they so desire. This also works when the suggestion is wrong: people may retract their close vote if the distinction is explained in a reply comment.

Answer 3

Bear in mind that when people go searching for duplicate targets we're primarily looking for existing answers that will answer the new question. It doesn't really matter much if the new question superficially seems different to the dupe target.

However, if you're new to the topic, the connection between the new & old questions may not be clear. In such cases, people posting dupe targets should use a comment to clarify that connection, either by editing the dupe auto-comment, or by posting a separate comment.

I certainly don't want to encourage people to post dupe targets that are not a good match for the new question. We should make an effort to locate the best target (or targets) we can find. And if the OP seems like they are new to the topic and the selected target(s) might be too advanced for the OP, add a bit of extra explanation so the OP isn't left with information that's technically correct but which they don't understand how to apply to their situation.