Does Mempool.space collect any kind of data about their users' search queries? And if so, is that data being sold?
According to early project contributor Emzy, no third party actor has access to the users' search queries. However, some data is being analyzed internally by the developers in order to know what to improve.
You don't need to trust Emzy, Simon, Wiz, or any other developer, though: mempool.space is free open source software that anyone can run on top of their full nodes. You can already download the Mempool interface on distributions such as RaspiBlitz, Citadel, Umbrel and MyNode. By doing so, you remove reliance on a centralized website while enjoying the pure awesomeness of the interface.