Make it easier to leave defaults defaulted after having merely selected a field

[nwinter]

With the new defaults, we often end up with a situation like this:

If I press tab or enter in order to save my edit by navigating away from the field, then I get this:

Now there's nothing I can do to avoid the maxAcceleration becoming set to 100 instead of being left as a default of 100:

After which I have to click on the field name (not value) and hit "delete" to restore it to default state. The only other workaround is to deselect the field by clicking with the mouse.

The result is that we get a lot of accidentally overwritten defaults.

What if instead we don't assign the values of fields if they are the same as the default? Or if we only do so when pressing enter, not tab?