Disable authors (or all users) delete discussion comments

One of our journals have asked for a way to disable the function for authors to remove messages they posted in discussions. They would be okay with disabling the delete functionality for discussion messages altogether.

Now I am wondering whether there might be a better and more effective way than getting all the CSS selectors for those links/buttons and include a CSS file to hide them into the backend as described here.

Any suggestions would be welcome!