...formally the question could be answered but it will not help the
Neither is it our duty to judge whether or not a question will help the asker, nor are we capable of making such judgements without more background information in most instances.
Should we accept that StackExchange is not a place to tell things like
With Stack Exchange strongly trying to enforce their new Code of Conduct, your comment (as described in the question) lies somewhere in the grey area. Depending on the person and situation, it could either be considered to be "helpful" and a cue (for the asker) to start learning quantum computing formally, or it could be considered to be in the "Unfriendly" category. While I cannot say why exactly your comment was deleted, in these cases I personally do not bother (after having several negative experiences in this regard, during the few years I spent on the SE sites) to make deductions about the pedagogy the asker is being subject to since there are too many variables involved. After all, Stack Exchange is about Q&A and ideally, we are supposed to take them at face value without making judgments (such as, whether or not answers to a certain question they asked will help them in the learning process) about the posters. In case the OP doesn't find the answers helpful they can obviously ask fresh questions with more details about what exactly they're looking for.
In short, while it might be tempting to give unasked-for pedagogical advice, even if in good faith, perhaps it is better to avoid it unless we're absolutely certain that it cannot be misconstrued as "Unfriendly". Moreover, trying to frame a comprehensive-and-polite-unasked-for-advice-comment which without doubt adheres to all the rules can be pretty time-consuming and I wouldn't recommend it as a fair use of anyone's time. Sometimes it is indeed better to walk away and mind our own businesses.
The comment was about another comment of the question poster which
boils down to "I don't want to learn mainstream quantum computing but
I want to understand quantum computing, give me an example I can
understand without learning".
That said, if you do find that the question in context lacks research effort or is based on non-mainstream theories since you mention that it asks for an example which the OP can understand without necessarily learning mainstream quantum computing, maybe mention ways in which the question can be improved (again, simply focus on the question at hand, preferably without making judgements about how the OP should go about learning mainstream quantum computing) in the comments, and also feel free to use the downvote and relevant close vote options, whichever you deem fit.