The metrics you use to attract investment are things like monthly active users, and whether a comment was deleted after it was made doesn't affect that at all.
From what I gather, a lot of Reddit usage comes from Google referrals, similar to how StackOverflow gets a lot of its traffic. If people leaving Reddit delete or scramble their comments (which some are definitely doing), they also screw up Reddit’s referral value and Google ranking, so Reddit has quite some motivation for trying to restore those comments.
