The closest relevant site policy is the on-topic help article that says:
Questions that you should avoid:
- Shopping or Hardware Recommendations
But I don't think that actually applies in this case. The question "What model laptop should I buy?" is simply too open to receive a decent answer. By the StackOverflow model, we want detailed and precise answers to well-formed and specific questions. On the other hand, when asking about the compatibility of a specific model, the answer is likely a simple "yes" or "no". So from the perspective of maintaining high quality questions and answers I don't have a problem with it.
Even so, whenever a user asks a question like this I usually mark it as a duplicate of this question on compatibility or this question on laptops and certification and let them know that there is really no definitive answer to their question other than "Try it and see." It is simply not that likely for someone with the exact same model or hardware configuration to come along and confirm Ubuntu's compatibility. So at the very least we should add a comment to the question letting the asker know that they may never receive a definitive answer.
Furthermore, I don't think Ask Ubuntu should end up being a hardware compatibility database. First and foremost, the StackOverflow model does not lend itself to database queries. Finding the compatibility of your specific model or hardware would probably be a nightmare using only the search bar. It would be much better to get a dedicated site to host a comprehensive (and potentially user-driven) hardware compatibility database. The Ubuntu Certified Hardware page is a good start, but is by no means exhaustive.
TL;DR Until a website comes along that seeks to create a comprehensive database of compatible hardware, I think we should tolerate these questions while letting the askers know that the best method is to just "Try it and see."
(NOTE: Edited significantly based on comments from @kos below.)
