Quality Assurance for Newbies

I don't know of such system but I've been pondering about the same thing (that could help with some of the quality issues we have in Haiti).

I guess that some email list might be a better place for discussing this (and it may well have been discussed already) but my thoughts:

You can always send a request to your local email list (or why not the main talk list?) for someone to review your changes. Problems with this are at least that this is not a "system" not at least a system with tickets (if that's what you were thinking of). Also, I can't think of a convenient way to review your edits; other than sending someone your .osm file (doesn't work with Potlatch edits). Your changeset history shows the bounding boxes of your edits so reviewing the area that you have edited to see if anything stands out (without looking at the exact details of your edits) is easy.

As per how to avoid mistakes, mess up anything or forget something -- it's practically impossible not to. The only way to avoid mistakes is not to edit. I've messed up a number of times and I don't know any mapper who wouldn't have at some point. So don't fret too much -- but do try to avoid messing up "needlessly" (as you are). And try to learn to identify your mistakes in your own review so you can correct them when you see them.