There are two main purposes for Stack Exchange sites:
- help someone solve a specific problem (or more generally, answer a specific question);
- help others with similar problems.
The second is captured more ambitiously in the tour as “With your help, we're working together to build a library of detailed answers to every question about Unix or Linux.”
I tend to think of the “problem can’t be reproduced” close reason as useful for questions which only serve the first purpose above (insofar as we can determine that). These questions, typo questions in particular, only need sufficient feedback for the asker to figure out what the typo was; once that’s fixed, there’s nothing further to fix and the answer is unlikely to be useful to anyone else. Keeping these questions (and answers, even if only in comments) only adds to the noise on the site.
I agree that the close reason could perhaps be rephrased. When I see
"Questions describing a problem that can't be reproduced and seemingly went away on its own (or went away when a typo was fixed) are off-topic as they are unlikely to help future readers."
I think of it as two entirely different reasons:
- problems which can’t be reproduced (with the possible reason that they went away on their own, which sometimes is nice if only to “save face”) — I get the impression we don’t actually use this all that often, in part I think because it discounts the asker’s experience which we assume is true (even if their account of it is flawed);
- typos, which obviously can be reproduced but are “unlikely to help future readers”.
Perhaps a better phrasing would be
“Questions describing a problem that can’t be reproduced (and seemingly went away on its own) or that can be fixed by correcting a typo are off-topic as they are unlikely to help future readers.”
As for how to deal with such questions, I think that pointing out the typo in comments is fine, for multiple reasons. The asker will presumably be sufficiently invested in fixing the problem that they’ll take the time to read the comments and find the typo; that addresses your point that “the mention of a typo appears only in the comment way down” (it also helps if people delete their obsolete comments, or flag others’ for moderator intervention). Writing up a proper answer for a typo would be counter-productive, because answers here tend to collect upvotes reasonably quickly if they’re correct, and upvoted answers prevent questions from being deleted.
