One comment can influence a life. It can start a career or end one. It can attract or repel, inspire or devastate. A casual remark made today may be recalled many years later with wonder, appreciation, or pain. Just one comment has started marriages and ended them. It can do the same with friendships.
Perhaps a comment should not have this much power, but it can. In many cases, the recipient can restrict or even eliminate the comment's impact. In others, there are few or no restraints on the power of one comment.
It is out there. For good or bad.