It seems like Ext.form.field.HtmlEditor has different behavior across browsers. For instance, in Firefox I can do the following operation: click on an image inside the html editor and a nice bounding box is displayed. The image can be resized. Please see the attached screenshot on the bottom of this report. The operation is not possible in Chrome 31 or IE 10.
With our editor we don't make any attempt to normalize differences between browsers (except for the lowest hanging fruits), rather we just wrap the native browser control & add the field interface to it.
If you're looking for something a bit more fully featured, you can check out some other editors, such as tinyMCE, CKEditor etc.
Twitter - @evantrimboli
Don't be afraid of the source code!