Try making some simple edits to this document:
http://mindprod.com/deepthoughts/musings.html
It is an unusually large document, 200K bytes, I grant you, but the editor becomes unusably slow.
I think the problem is you might be maintaining the document internally in the HTMLValidator editor as a giant Unicode string rather than a tree as is traditional for WP applications. Every time I hit a key, I suspect you must shift hundreds of thousands of bytes of information one slot right.
I have a quite new dual CPU motherboard. I have not seen this sort of jerkiness since the early days of the XT and MSWord version 1.0.
To fix this might require a major rethink of your internal document model, but the advantage would be in the editor would become really snappy for all documents.
Another thought is to have a dual model -- what is visible and what is not, and update your invisible part separately, the way you do now, but update in the background on a separate thread so the the screen feedback is not delayed.
I suspect you might tell me that I deserve dreadful response for the sin of creating such a huge document. That particular document could be easily split, but others I have cannot, such as 400K colour swatch tables:
http://mindprod.com/jgloss/x11alpha.html




