I was one of the reviewers who rejected it, so here's how I looked at it.
###General Philosophy
There are some other dimensions to the decision than old vs. new.
- Does the edit make the question better in a non-trivial way?
- Does the edit warrant bumping the question?
Improving a new question can help to get it answered. There's nothing wrong with trying to improve an old question, but bumping questions tends to steal oxygen from new posts so edits should accomplish something useful, like:
- attracting answers if unanswered, or attracting better or more current answers
- making a question clearer or easier to find if it is something people will be looking for or it could be a useful resource.
To the second point, questions that don't justify closure seem to fall into some broad categories:
- Useful resources
- OK questions that are not currently useful or relevant
- Questions that meet the minimum requirements to avoid closure/deletion but are basically flotsam
Questions in the last category won't be useful resources no matter how much you clean them up or make them easier to find. Questions in the middle category are more of a judgement call. I tend to avoid bumping questions in this group if they have long been inactive due to content rather than problems that could be fixed with an edit, and which are likely to go back to being buried on the site and unreferenced after the edit.
These are the kinds of things I look at:
How old is the question and when is the last time it had any activity? Is it likely to attract future activity?
Age is not a criterion except in the sense that the older a question is, the more likely it is to have age-related factors that might make it currently irrelevant.
Is it still relevant (is the software or hardware still in use; are answers applicable to current versions if it is; etc.)?
How useful was it when the question was fresh (votes, views, favorites, comments)?
Are the answers useful and consistent or did it attract a motley collection of low-quality or conflicting answers?
If the question is unlikely to attract new answers and the existing ones aren't useful, what's the sense of making the question easier to find?
How useful is the question and how clear is it?
Might improving and bumping the question attract new answers?
Might improving the question make it a significantly better resource if the information is "timeless"?
To what extent could the question use improvement and how much of the obvious improvements does the edit accomplish?
If the question needs a lot of work but the edit fixes only one item of low-hanging fruit, the editor should be encouraged to do a more thorough job. That encouragement, or lack thereof, will affect the quality of future edits.
There is also a question of whether the edit serves a useful purpose. Some polish consists of trivial improvements that don't really affect the utility of the post. Whether these make the post better is questionable.
###The edit in Question
Bringing this back to the edit mentioned in this Meta question, that question struck me as a low value, low priority thread that was already answered and probably wouldn't benefit from bumping. It also seemed unlikely to be attracting many future views. The title edit was an improvement, but the original title wasn't so bad that it was a serious problem. I didn't think the change would make a substantive difference in the utility of the question.
Sometimes on a question that strikes me as having little current value, I approve the edit if somebody invested some time to polish it into a gem. I assume that if it was that useful to them, maybe it will be useful to others, as well. In this case, the only thing improved was the title, and that didn't seem worth bumping the question.
###Exception for thread authors
At review time, I hadn't noticed that you had provided an answer. Authors of answers often want their answer viewed in the best light, and want the question in the best shape it can be to attract viewers to the answer. If I had noticed, and the edit had been a little more thorough, I probably would have approved it. If you think the thread is still useful and want to take another shot at it, give it another go and polish more than just the title.
###Example of title edit approved for old question
Here's an example of another old post (6 yrs old), where I approved a title edit only: http://superuser.com/review/suggested-edits/625545.
The question attracted 14 upvotes, 8 favorites, and almost 13K views. There is an accepted answer that attracted 18 upvotes. There has been recent activity. The question could use a little polish, but has no issues that prevented it from being useful. The title was awful, but the thread managed to be useful and attract a lot of readership despite it. This thread is a resource that appears to still be relevant, and just a title edit made it more useful.