I read that - thanks for clarifying! I'll post here so I'm not jumping in your convo.

For me, it's a pair of simple thought processes. We're called to pray for each other > The prayers of the righteous are valuable > The saints are living witnesses = It's okay to pray for saints.

Second, we see that Mary has /some/ special place. Being called κεχαριτωμένη, the contrast in typology to Eve seen with her being called "Woman," her lack of earthly death, the way Christ entrusted her to the Apostle John as an adoptive mother suggesting that she is a spiritual mother who cares for us. So, placing her above the other saints seems fitting.

I think it can be taken too far (just like any good thing; a devotion to icons or a focus on the letter of the law). But our belief that she is sinless is more focused on who she is, rather than our desire to have her intercede for us. I don't know that it would really degrade her place as the greatest of saints if she had sinned. The sinlessness really comes from a combination of how the angel addressed her, the typology she represents, and the traditions that followed in the early church. I'd argue that, even if saintly intercession weren't a thing, the idea of Mary's sinlessness would still be a widely-held and fitting concept.