Short description
The idea is to put a second "edit page" link on the pages, that would read "minor edit" or "correct typo" or "trivial change", something like that. The rationale behind this is that people rarely use the "trivial change" checkbox, because at the moment it's displayed they already think about the content.
An average human reads the page, sees a mistake, hits "edit" and then he's too absorbed with finding the fragment he wants to correct, correcting it, looking at preview, saving the changes, etc. to really care about the little checkbox.
On the other hand, he usually knows (and thinks about it) whether he's hitting edit to make a trivial change or to add some meaningful content. Of course, as he edits, he might change his mind, so the checkbox should stay.
The only difference would be it's initial state.
What about simply offering two save button? That would be more visible than the check box. Also moving the UI Elements at the bottom to the top could help...
I think the only moment when we can catch the user actually thinking about what he does is before he starts editing. The rest is just a habit, a reflex, no matter how many buttons there are, he'll always hit one and the same - whichever one he's more used to.