QGIS » QGIS Application

Hi,

I think this is more a feature request than a bug report, but feel free to change if you think Bug Report is more appropriate.
A great feature in QGIS is being able to open the same layer many times (or duplicate it) and use the one layer for multiple types of styling or looks (particularly with the inverted polygon styling ability). But this does open up the risk of someone inadvertently toggling editing on for the one layer more than once at the same time.

It would be great if there was a little message box or warning that prevented a user from making a layer editable if another instance of the same layer is already in editable mode.
We have had users on occasion accidentally do this and it nearly always results in major corruption of the file.

While it is quite clearly user error, it is very easy to do (even for experienced GIS operators!) when you have very large projects with many layers open.