I don't think that's true of most people. People use IANAL defensively in an attempt to avoid embarrassment from being shown to be wrong in an ensuing discussion as opposed to a "free to present my opinion without scrutiny" statement. Most scientists have this too amongst a group of their peers (in conferences for example), they offer a lot of caveats in contributing to discussions that even though are primarily their realm of expertise, they may be out of their depth in the room.

If seeking validation is the prime motivation to contribute to a discussion, at the very least I think HN is the least guilty of this amongst most forums.