On a less serious note, editing can be fun for in-jokes and has become something of a staple with select users, whether we like it or not. Some users are so addicted to messing around with other posts that you'd literally have to demote them to guarantee they'd stop, so on a "for fun" level, this issue is almost non-negotiable.
However, I believe many of us know that, when a pressing issue arises on META, some users feel the need to "persuade" an audience to think something different by changing or straight-up editing out the original intention of an important post.
Those situations are so rude, disrespectful, and completely not okay, that I can't believe I'm addressing it.
It all depends on the situation. Strictly saying every quirky edit should be reported doesn't make as much sense as, say, reporting a slandering edit or an edit that takes away from the original post's integrity. It's a case-by-case deal, so I suppose the best rule of thumb for this would be to report anything that personally offends you or made your service worse off. At least then the member can get a friendly warning or a talking-to.