You are right that the line between general and personal interest in Spanish SE is very thin. Most of the questions (if not all) of this user are about a document he is translating. Some of his questions are about technical language, which might be useful for other users and welcome here.
However, the question I closed is about how can he improve his sentence in its context, so I don't see how it can be useful to future users. It's true that there were no close votes, but there aren't any reopen votes as well. As a moderator, I only applied the rules proposed by the community here in meta (not even StackExchange). The rest of the questions of this user that I had not so clear what to do, I let the community decide.
If you think that we should let ask questions about "translating and correcting sentences", you can open a question in meta and let's see what the community thinks.
TL;DR: I closed it because it's asking an opinion about a particular sentence, and I think that it won't be useful for future users.