You're right. I'd hate for my comment to be deleted just because I disagreed with the OP. Not saying that many on Hubski would do that, but someone out there is bound to. If we're trying to foster discussion, letting OP delete specific posts could potentially skew conversations in his or her favor.
But that disagreement between OP and the commenter is what garners discussion. If OP wants an interesting thread full of lots of comments, OP is going to have to leave the posts he disagrees with alone. If OP wants to only speak with those he agrees with, then the thread will be lame and have very few comments. Sure, your comment could be deleted because OP thought you were annoying. But in deleting one comment, how many others could OP have deleted?
I hope we are not allowed to mod our own posts for exactly this reason. In fact, I've wondered many times about the opposite. What if after a few hours, you couldn't even edit your original post? (A little time to catch typos, etc). I don't think I can count the number of times I completely disagree with the OP, or commenters shred me to pieces... And I love it. Not agreeing is why this place is fertile soil.But that disagreement between OP and the commenter is what garners discussion.