I don't have a background in linguistics, but to me the above seems odd for some reason. Why is a subject "we" necessary? "to make sure it works" is an adverbial phrase headed by the to-infinitive (to+make sure) and modifying the main phrasal verb (listened to). Adverbial phrases function like adverbs, often specifying manner, extent, reason, etc. A simple test in this case is to ask the question "why" after the main clause and see if the following phrase answers it. If it does, it's probably an adverbial phrase. Consider:
I exercise (why?) to lose weight.
The eggs were broken (why?) to make an omelet.
The CD must be listened to (why?) to make sure it works.
Grammatically, your sentence is fine. Stylistically though, it's a bit clumsy to double the "to", which is why you're having the "this sounds weird" gut reaction. Commas and pauses are a good idea, as has been suggested. Sometimes, the doubling is necessary and commas/pauses are the only way to help, as in the following focus-providing pseudocleft:
What it is, is a bad case of the flu.
In your case though, you can avoid the whole mess and follow the moderator's advice.
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