I agree with Leaffan (at least, as far as this issue. The Leafs? ehhh…) Someone stupid enough to build a pool and fail to comply with obvious safety regulations, and then give you grief about mentioning it, is possibly equally likely to do things up to and including rocks through your window, slashed tires, etc. Never underestimate the power of assholery, especially if you both have to live there for the foreseeable future.
Seriously, are there people who DON’T know a pool needs a fence? That indicates a level of stupidity that few can rise to. This is not “please trim your tree” or “weed your lawn”. This is a potentially lethal situation.
Most police will not tell someone who filed a complaint. Of course, the policeman may say something like “your broken pipe can be seen and smelled next door” or something equally clueless and clueful. But generally, they will not disclose something about a complainant. (If they do, complain some more… to the police chief.)