Good concern to have—IF (per your drawings above and earlier posts) that wear mark is under your stem’s clamp area (so ABOVE your headset bearings) then your stem contact area is big enough that a narrow depression like that is manageable—there are stems out there with much lower stack heights (and thus contact area) than the one you have and they still manage just fine. But if (as I’m reading your latest post above) the wear mark is IN the headset area, that’s a whole different issue as your headset bearing (race) would be what wore that groove and will no longer be tight to your fork—you’d have a gap (‘slop’) in your top bearing area. No epoxy will help there as it would wear out faster than the carbon before it. That’s a much more difficult issue to solve for—the most direct solution would be to go with a different fork. Since your preferred set up is putting so much torsion on this, maybe opt for an aluminum steerer in the replacement fork?
Last edited by Sonofamechanic; 05-07-22 at 06:02 AM.