>>> We also used a set of criteria to identify and exclude suspicious responses: [...] Surveys from identical IP addresses, as well as surveys with responses that were overwhelmingly similar.

That one picked my attention.

All developers in a company are behind a single NAT IP. It's a pretty bad idea to deduplicate based on IP.

I'd hate to find out that my answers were ignored because another coworker also filled the survey. We probably all received the same survey email the same day.