It hasn't been a problem thus far, but we'll keep an eye on it.
As for why it's like it is....
The Terms Of Service (viewtopic.php?f=8&t=2
) actively encourage people to self-moderate and sometimes what seemed like an appropriate or decent comment at the time, might seem tasteless, tactless, irrelevant or distracting when viewed later with fresh eyes. We like to put trust in our members that they will do the right thing and take various factors into account when editing or deleting their posts, such as the issue of continuity which you raise here. To empower people to self-moderate as they think is best, and take responsibility for their speech, they need to be able to edit their posts.