I'll just give you an example here, Beloved.
Say I'm a troll, and I post something ugly to you. Then you, taken aback, say something in retaliation. I then edit my initial post, to say something nice to you, and report your post. The mods come along and see the following exchange:
JimJimmers: "Have a nice day, HisBeloved1! God Bless!"
HisBeloved1: "You foul-mouthed filthy creature!"
Hence, the mods set the editing limit at 5 minutes, to prevent them from having to spend hours trying to figure things like that out. We get a few trolls who like to stop by and keep thinks interesting.