I have originally disabled ExcludeHTMLImportConverter in designtime before this post. I have now added rvc.ExcludeHTMLImportConverter:= true; during runtime with the same results. It doesn't work for me..
I can see the problem that assigning this property when the list of converters is already loaded does nothing.
However, when assigning at designtime, or in runtime just after creation of the component, it works correctly.
Try running ActionTest exe demo from the web site.
How many "HTMLs" you can see in "Insert | File" dialog?
If ExcludeHTMLImportConverter works, there will be only one (for rvHtmlImporter). If it does not work, there will be two items.