Am I persuading people with polish instead of the truth?

It is a good sign that you even ask this. Plenty of people never wonder whether their gift for making things persuasive has drifted away from what is true. The fact that it nags at you means your conscience is still awake, and that is worth more than the skill itself. Polish and truth are not enemies. A clear, well-made presentation can serve the truth by helping people see it who would otherwise miss it. The danger is only when the shine hides a weak fact instead of revealing a strong one. The tool is the same; what changes is what you are pointing it at. So make truth the test that polish has to pass. Before you finish, ask: if I stripped away all the presentation, would the plain facts still hold. If yes, your skill is serving the truth. If you flinch, you have found the thing to fix. Keep asking that question, and you will not become the thing you fear.