I feel like I must point out something here, and let me take How to obtain the result of a chemical reaction given two components?How to obtain the result of a chemical reaction given two components? as an example.
Just because someone is asking for a tool to solve a problem, doesn't make it the kind of question we don't want.
Semyon is explaining a very specific, niche problem, which he likes to solve. He assumes that there would be a software that is the solution. A question like that is perfectly valid for Super User.
"What's your favorite text editor?" and "What tool can I use to convert CommonMark to XPS?" are very different questions in our software recommendation context.
We always knew that (especially for new users of the site) this is a very fine line and it's hard to judge if a question is valid for us, but the rule always was "Can the question be rewritten to ask for a technique rather than a tool?" If so, then it should be rewritten. If not, then it's probably not right for us.
That being said, I'm all for cleaning up this tag and, ultimately, removing it from the site. But this is a very delicate tag to clean up.
This is not our regular cleanup job where the primary goal is the removal of the tag from the question and cleaning up small content issues. We're talking about removal of complete questions from the site.
You have already mentioned it and I'm going to bring it up again as well. Historical significance is very important in this. We like people visiting our site. If there is a question that isn't right for us, but has 1500k views, then there is a good chance that we'd like to keep it. Questions like that should be locked for historical significance and not deleted. software-rec should obviously still be removed from the question.
While on the subject of deletion, the questions that we want to get rid of can't simply be closed. They need to be deleted. This could mean a lot of flags, because I don't see how else we would get rid of them.
Ultimately, we want to save every question we can. If it can be rewritten to suit our site, then it should. Example: http://superuser.com/posts/324051/revisionshttps://superuser.com/posts/324051/revisions