Hm, i suspect this issue also related with your server blocked or restricted the POST data can't contain
http:// based on what i tested on your site, it seems like your server detected there got contain this
http:// data, then it will fall back to 406 error.
You can refer on my attached screenshot below.
Even i try add
http:// in other field, it also hit the same issue.
The reason why you doesn't hit this error is because your current .htaccess do something do not render the real server message on the page so it will redirect back to your site Easysocial dashboard page, by right it should redirect back to the user profile page.
Once I rename your .htaccess file temporary, then access this non-sef profile page url
[gist type="php"]
https://www.riskoracle.com/index.php?option=com_easysocial&view=profile&layout=edit
[/gist]
it will show the correct error once you add
http:// this word into one of your custom field and press save button.
Can you consult with your webhosting provider regarding this and see whether they know something about this?