Very interesting.
Regarding the final line "Glad to see where you stand on knaves and miscreants!", it might be a comment about self-preservation since we know that Astarion is hiding some facts from us (yknow like the entire vampire thing, early). I wonder how much weight ones dialogue options actually carry, because if Larian is picky; then that option alone could dictate how easily Astarion comes forward with future... Confessions.
Regarding the other options; this is not the first time we see some conversation that *could* be interpreted as a "kinder than he looks"-kinda thing, and I look forward to seeing more! Larian has promised us some compelling character development, so I think we'll see plenty os "Sebilles" in BG3.
Thank you very much for sharing!