Does the Email Template Customizer strip classes added manually or via hooks?

Hi Villa theme!

We have another plugin (the handy Flycart Discount Rules plugin) which includes a neat little “You saved $xx.xx” message in the cart and near the Orders total as a customer checks out, etc. We love this. However, it is also included in the email right near the order total and it appears that any custom “classes” that get added *might* be getting stripped by the Email Template Customizer. Do you know if this is the case by chance?

I made a video for us to see what we are hoping can happen: https://share.getcloudapp.com/7KukRjxq

After watching the video, would you happen to have any ideas on how we can solve this, if indeed it might be possible to use both plugins for this?

Thank you so much!