Some of these questions discuss whether or not it makes sense, or what to do when the supposed proof tries to prove a famous open problem, or how to even answer such question, or how to make them more attractive.
These are all valid concerns. But most of these were asked quite some time ago. And the growth of the site makes it harder to fix any future damages, so I think we need to talk about this again. In this question, I am not offering any solutions. I just want to highlight the problems and bring this back to the table, and engage with a discussion on what are possible solutions in the answers below.
I had recently asked a user who had been posting a lot of fairly elaborated proofs (sometimes in response to suggestions on previous questions). With a little discussion in the comments, this is what I managed to extract as far as pros to proof verification questions:
Not everyone in this site is a student, not everyone has a teacher, assistant, or a grader to check their work and make remarks. Many people here are hobbyists or self-educating themselves, and they need help from others to make sure that they are not making mistakes in their work.
Supposedly, there is a contribution of an elaborate proof to the corpus of proofs on the site. This helps future visitors, since they can find this proof and learn from it, and learn from its mistakes if those are pointed out in the answers.
In one instance, the proof seemed fine, and even one person said it's fine, but then someone else pointed out a subtle mistake. Which requires closer attention to details. This is something you might not be able to do yourself if you're asking these sort of verification related questions, and this is how we truly learn mathematics.
On the contra side:
Future visitors will also want their proofs to be verified. They will simply post their proof, and this will not be a duplicate, because the question is not about the problem, but rather about the solution, which is likely to be somewhat different than the previous instances. This leads to an inflation of questions which are asking essentially the same, but are not "formally duplicates".
It might be that someone looks at the proof says "Yeah, that looks good", but they glanced over the details. In that case, especially if this user is more established, any mistake might be overlooked by future readers. (The issue here is that finding a mistake is a $\Sigma_1$-type problem: until you found it, you don't know if it's there.)
If you are looking to contribute an elaborate proof, then you're looking to contribute an answer to this website. Not a question. It is far more reasonable to post the suggested proof as an answer to a question about the statement you're proving (or post a question and an answer if there is no such question). Of course the problem is that not everyone bothers to read the answers, you cannot award people a bounty for proof reading your answers, and so there is no "points incentive" for people to engage with your answer. This is why sometimes a user would post an answer to their question after receiving a partial or broad-strokes answer, and a few days later move this to a proof verification question, where they can incentivize more people to look at it.
What do you think we should be doing with proof verification?
The issues here are that the site is growing fast in users, and this means that it grows even faster with more questions. If we decide that we enable a proof verification culture, this might cause an even more serious problem in the future in the form of repeated questions with the same proofs.
For example "Posts containing 'algebraic numbers is:q'" show $9$ questions, out of the first $10$, asking to verify the proof that the algebraic numbers are countable.
This will continue to blow up, rapidly. Whereas the problem with "homework mill questions" (for lack of a better term) can be solved by dedicated people who point out duplicates and close those questions where the OP is truly disinterested in providing any contribution, proof verification are hardly like that. The OP usually shows their work (often to a degree one might call excessive), and seem to be willing to contribute to the site their version of the solution.