For me that scene with SH fired only once, out of all playthroughs. Only Karlach seems to notice an ongoing Astarion-mance in my runs. Freaking weird. I believe banging Astarion BEFORE the party causes some of these bugs...
I got the reactions from Karlach, Lae'zel and Shart but also only when not having slept with Astarion before the party and in Lae'zel's case only if I also hadn't talked with her about spending a night together before the party.
