Hi Danail,
I was caught up with something else and couldn't reply earlier. Unfortunetly, the issue I was having with <button> tags being stripped by the editor still exists... Here is how I can replicate the issue:
* I have a SharePoint 2013 web part page with the subclassed control as mentioned in this post.
* I go into HTML mode and enter <button>Test</button>.
* I click on the link "Add a web part" as present on the web part page and add any web part. I then chose to "Edit the web part" using the web part's drop down menu and in the web part configuration section, I click "Apply" or "OK". This cause a postback of the page.
* The content in the editor has now changed to "Test" without the button tags..
Any ideas why this is happening? I have set the following the config file during troubleshooting without any success:
<property name="AllowScripts">true</property>
<property name="ConvertToXHtml">false</property>
<property name="ContentFilters">None</property>
<property name="AllowSpecialTags">true</property>
Thanks,
Rajesh