I miss a user (now showing name user120647)'s answers to my questions. His answers would somehow always help me. But looks like he has disappeared or quit intentionally. Where's he?
Here are a few questions where he answered:
What you are seeing is the result when an account was deleted. Accounts with more than 500 reputation cannot be deleted by moderators, but only by the owner (and Stack Exchange itself, who hardly ever does this). As for reasons and what happened, nobody can give you a substantiated answer here:
Moreover, if anybody shared some knowledge or gossip about the situation, the account owner would have no means of sharing their version of anything, which would not be nice or fair.
Also see: Why we don't keep public records of suspensions. While this is not a suspension, similar thoughts apply.