I looked at the source of the add-on and found HTML classes that I could use for a userContent.css and fixed it for myself with this:
@-moz-document url-prefix("moz-extension://ffd499d6-b82e-4bcb-ba7b-9ffb92c168d4/popup/index.html") {
.bit-tooltip-container,
.bit-tooltip {
display: none !important;
}
}