Corrupts textarea field if its contents are annotated

I was demonstrating Hypothes.is to a colleague using the Tiki Wiki CMS Groupware web application engine. I annotated a word part of the default wiki page, then went on to modify the wiki page, to show that Hypothes.is deals with changes to the annotated text.

To my great surprise, in the textarea input field where one modifies the page's content, the annotated word disappeared. Saving the page did remove the annotated word from the page's content.

This happened with Tiki versions 15, 16 and 17, using Google Chrome versions 60 and 62 with extension versions 1.48.0.0 and 1.50.0.0, on 2 Windows machines. This reproduced whether the page's content was French or English. I however only reproduced this on local Tiki installations, except for a demonstration instance. I created [a page called "HomePage2"](http://jmorris-11758-6403.show.tikiwiki.org/tiki-index.php?page=HomePage2) in that instance using the default contents of Tiki's homepage.

To reproduce:

1. Create or edit a wiki page to contain the contents of the default homepage:
2. Activate the Hypothes.is extension
3. Select the word "configuring"
4. Submit any comment:
5. Click Edit to go to tiki-editpage.php?page=HomePage:
You will notice the word "configuring" disappearing during page load. If you save, you should see: 
If you then go to the history, you can confirm the corruption [comparing versions](http://jmorris-11758-6403.show.tikiwiki.org/tiki-pagehistory.php?page=HomePage2&newver=0&oldver=1):

The HTTP credentials to enter the demonstration instance are "show"/"show". The password for user admin is "12345".

I did not investigate why the word is removed.