Hi Stefano,
May I know the reason why you would like to hide these 2 buttons?

Unfortunately there are no setting in the admin panel to disable these 2 buttons. However, you can still achieve this by using a template override.
You can refer to our guide on template override here.

You can use the file that I have attached which is modified to hide those 2 buttons. Place the file in JoomlaFolder/templates/yourCurrentTemplate/html/com_easydiscuss/post/default.replies.filters.php

Can you also provide us your backend and ftp access in case you need more troubleshooting from us at http://stackideas.com/dashboard/site ?