An interesting point, Frankenstein, and one that potentially opens up a vast field of philosophical, moral and cultural questions about the nature, development and possible consequences of our post-Gutenberg epoch of written communication by electronic media.
But I must duck all that and just say this: I believe we trust that members of this forum mostly exercise a good amount of honesty, integrity and empathic consideration in their posting. If a pivotal meaning in a post is to be altered, then surely a new post is warranted.
However there is here, as in society generally, a minority who seek to subjugate, mislead and manipulate others by means of "gaslighting" and other deeply dishonest styles of communication, and who will not hesitate to edit vital meanings in their media posts just in order to sustain a blameless facade. But unfortunately for those toxic few, I notice the habit of quoting posts when replying or commenting is widespread here; I see that as an excellent and healthy means of forfending against gaslighting and other toxic forms of dishonest communication.
Using post-send editing to deal with "oops" events is becoming commonplace in text forums. But I regard the 15 minute time window allowed for this in iMessage and WhatsApp for example, as too often too short for this forum which frequently deals with technically and artistically highly complex topics. After all, isn't this supposed to be a place in which smart, cultured and creative folks choose to communicate?