When adding a closure, I think it would come in handy if there was a comments field (or text box) that could be used to let other editors know, what source was used. If there is a problem/question afterwards, other editors know where to ask for additional info.

This field should only be visible to editors, no need to show it in the Waze app itself.

Currenly I use the description field, but that's not so handy.