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.
"Do not force others, including children, by any means whatsoever, to adopt your views, whether by authority, threat, money, propaganda, or even education." - Ven. Thich Nhat Hanh
"Whether I were to preach in brief, Sāriputta, or whether I were to preach in detail, Sāriputta, or whether I were to preach both in brief or in detail, Sāriputta, rare are those who understand." (A I 333, Sāriputtasutta)