The question Can I get some tips or criticisms of this couch plan? looks like the user account has been deleted. Is it a waste of effort to answer this? Especially since it would only serve the OP, and his specific plan, so I don't see this having community value.
It was a migration from DIY.SE from a user that doesn't have an account linked to one on wooworking.SE yet.
The original user will be notified that the question is migrated and will get a chance to link his account to the one asking the question.
Since ratchet freak addressed the case for this question specifically. Generally, a question that only serves the OP is not on topic on SE sites, so it should be put on hold and then closed.
If a user were to ask a good question and then delete their account, it's definitely good practice to answer it as best as we can. The mindset you should have is that we're answering questions to primarily help all future visitors to the site, not just the OP.