If the section has a bullet point in front of it then it cannot be edited because separating the section out will break the LIST tag. When I have such sections in my wiki, they don't even offer an edit link. This is the expected behavior. If you are seeing an edit link for a section that cannot actually be edited, then you will have to PM me a link to it, because you should not have that option.
When I refer to garbage, what I mean is that users use WYSIWYG mode to add markup without seeing what is actually going on in the code. Sometimes you end up with empty bold-tags that are just there for no reason, and often you end up with bold tags wrapping other things that from a spec perspective are not supposed to have anything wrapping them. Sometimes you have something that looks fine in the WYSIWYG editor, but as soon as you submit, it looks like the entire web site exploded.
The vw_section_missing_error is a response where the wiki has detected that if you do this, the web site will probably explode. If you get this error, you should edit the full article, not use WYSIWYG mode, and clean out the broken code.