I only see 1 question in your history that was marked as a duplicate. This is the one you're referring to? check if string represents valid path in BASH. This question was closed by a single user who has a gold badge for questions that have been tagged as shell-script.
Generally it's the case that it takes 5 votes from user's to close a question as a duplicate, or if a moderator decides to do so. In this case given this user has earned a certain amount of score for answering questions with the shell-script tag, they're awarded the privilege of being able to automatically cast close and duplicate votes that are binding, and have an immediate effect.
As to your options:
- If you need to alert a mod for any reason you can always select the flags link under a question or answer and then select the "in need of moderator intervention" option and write a custom note to us.
- Leave a comment directed to this individual using an at sign + username i.e. "@their-username", under your question. When you own the question you automatically have this ability even if you do not have enough rep to leave comments anywhere else on the site.
- Consider adjusting your question so that it is more specific and is no longer covered directly by an answer to the duplicate that it was linked to.
This 3rd option is typically the problem with many questions that fall into the realm of being marked a duplicate of another question. They typically lack enough specifics that make them standout on their own, so that an already pre-existing answer on the site does not fully cover them.
Incidentally, our help section in the upper right hand corner provides much of the details that I've mentioned as well: https://unix.stackexchange.com/help/duplicates. Also this meta covers the privilege: Increase close vote weight for gold tag badge holders.
Here's where you click the flag link on a question.
And here's the resulting dialog, where you can select to alert a mod.