It might be other platforms not saying a comment has been deleted or users here being more likely to engage with content and delete it for various reasons.
For example a post said “What was wierdest gift you’ve received this years?” and someone may have missed the this year and told a story about a prior Christmas. They could have also accidentally replied to a different comment instead of the post itself.
Lemmy also uses up and down votes like Reddit so maybe they got a few too many down votes and just deleted it.