In the interest of making the internet a better place, some time ago a feature was added whereby old, off-topic questions that had stellar information in them could be un-deleted, and locked, with a message that read in part
This question exists because it has historical significance, but it is not considered a good, on-topic question for this site, so please do not use it as evidence that you can ask similar questions here.
A good example of this in action is with the strangest language features question
I think we should allow a broader range of locking behavior for other valuable, yet off-topic questions that aren't necessarily of historical value. In particular, when looking through my favorites list, I was sad to see that this question on Backbone.js vs. KnockoutJS (Stack Overflow 10K only) was deleted. Trying to figure how Backbone and KnockoutJS compare/complement each other is an extremely common search for web developers, and the top answer to this question is simply the best of anything I can find from Google—which is why I favorited it.
Ideally, I'd love to see this question undeleted, locked, but with a message that says something to the effect of:
This question, while off-topic for Stack Overflow, was asked in bygone times of looser standards, and happened to acquire great answers before being deleted. In the interest of making the internet a better place, it is being left open, and locked. Do not use the existence of this question as evidence that you can ask shopping questions on Stack Overflow; you can't.