I would just say that using a comma to declare many variables is a bit obscure. Maybe if you were doing them all on one line you could argue that it's tidier. e.g.
<pre>
var minX, maxX, minY, maxY;
</pre>

But given that each declaration is on a new line anyway I think this is more consistent and less likely to cause confusion:

<pre>
    var me = this;
    var dom = me.el.dom;
    var maskMsg = Ext.Element.data(dom, 'maskMsg');
</pre>

It is up to you if you want to make the change. I'm going to merge the rest of your changes anyway.