This causes me to have to add CSS to overwrite all this, because it is too much work for our editors to filter this from the HTML. Why does the editor automatically add this?

One example is <span style="font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif; font-size: 13px;">

All our texts are supposed to be Exo 2 and 14px. The default Freshdesk setting is Source Sans Pro. My colleague did not copy paste the text from anywhere, so I am wondering where Helvetica Neue comes from.