Hi there @redeyedrocker,
Thanks for confirming that. Looking again at your form, I’m seeing that the yellow background is coming from your user agent stylesheet:

Full Size: https://d.pr/i/rnwjIl
This is a default stylesheet that is built into your browser to provide basic styling to basic HTML markup tags. It overlays this styling over any website you visit. More on that here:
https://www.geeksforgeeks.org/what-is-a-user-agent-stylesheet/
Overriding or disabling that style sheet can be a challenge. I’d recommend inserting a custom CSS rule to your theme (for most WordPress themes, this would be under Appearance > Customize, then choose Custom CSS) that will force any highlighted text to not use the default coloured background.
CSS of this nature might look like this:
mark {
background-color: transparent !important;
}
Please note that custom CSS of this nature is offered as a courtesy and would not be officially supported should you require additional help getting it to work with your theme.