No such thing as “deep-seeded”
Deep-seeded vs. deep-seated
Deep-seeded almost makes sense in a metaphorical way (though seeds sown too deeply won’t grow), but deep-seated is the term you’re looking for. The phrasal adjective (usually requiring a hyphen) simply indicates that something is seated (in the sense fixed firmly in place) deeply in something else. The OED defines it as having its seat far beneath the surface.1
This is a special thread for those who go on rants and actually call people vile names for their typos. When those people are actually using things grammatically incorrectly all the time.
You know who you are.