There's a limit to how much help you're likely to get to improve a questiion.
Your initial question here on meta was a good idea - your HAProxy question on the main site wasn't well received, so asking here for ideas on how to improve it is an acceptable thing to do. You got some answers and made some changes.
Then you wanted to ask why your HAProxy question got downvotes after you changed it. There are no here guidelines that I know of about whether it's acceptable to ask "how can I improve my question even more?" but it's probably not a good idea. Chances are, anyone who's going to help you would do so after the first question, it's unlikely that someone would come along and see the second one but not the first.
In this case, it wasn't very long between the first and second meta question, so it makes sense that the second was closed as a duplicate of the first.
The comment about not changing your question too much was refering to the way you changed your first meta question to be about the new situation, and it's a valid comment. On SE sites it's not considered to be acceptable to change any question so much that existing answers aren't valid.
In summary, you're better off only asking for help once on meta about how to improve a specific question. If the advice you get doesn't result in the question being improved enough to get significantly more upvotes, then you should just move on.