akom
It saves your html fine, but you can't edit it anymore unless you paste the whole thing in each time.
There is an error in your review. The word textarea in the first sentence after "contains a" is omitted.
The textarea in question is on the parameters of the module backend. The module editing page is just a web page like any other.
The issue at the heart of this is that in ordinary web pages form elements wouldn't contain other form elements.
The text box is defined by a textarea tag. So browsers being designed to be tolerant of faults treat the opening of inserted content tag as a closing one and the whole thing snarls up.
This isn't just a problem with my module or with Joomla but is of wider application.
There are workarounds for using textareas but of none them are very neat.
This module is intended as a flexible lightweight extension, and as such I believe it would be wrong to extend the code significantly inorder to overcome this issue.
There are better and more secure answers for putting forms on Joomla pages than using this module or others which are similiar.
I would direct users to the specific forms sections on the Joomla extension pages.
Specifically Core Enhancements->Data Reports and Contacts & Feedback->Forms.