Friendly, short mention: there is an objectively severe violation of basic BDSM etiquette in AA scenes, which is what some people are uncomfortable with, though they don't know how to put it into words.
(Addition: "consent" as a legal term ≠ "consent" in BDSM etiquette. It's consent legally + additional standards, hence: "safe, sane, and consensual". The law does not care about safe or sane until you kill someone).
Faerun isn't a setting that has a 1:1 understanding of BDSM, however. Real life standards for acceptable behavior and what some people do in fiction, such as Balder's Gate and yes, even 50 shades of grey, rarely end up comparable. If you met someone with as lousy an etiquette as Astarion in rl, you should run for the hills. If he's found in a book set in modernity, you should blame the author's understanding of the subject. If set in ancient times, it becomes more complicated.
The current angle of the romance will no doubt be immensely upsetting for a portion of people to play who are not into unnegtioated D/s. Yes, they may ask for the removal of what upsets them. It's Larian who will have to set the balance -- or alienate that segment of people otherwise interested in the romance by choice.
There is an objective basis for complaint: the content of the game does not measure up to modern understanding of safe, sane and consensual. There is no negotiation of kink. As said, it's also a fantasy setting, so discrepancies in this regard are "normal" in the sense of "average". It's not usually worth critiquing, unless it gives a lot of people a woefully wrong perspective on BDSM. I don't think many people are using Balder's Gate 3 to get into the scene, so I'll personally let it slide, but I also doubt anyone is going to laud the romance for being a realistic, *modern* portrayal. It's a complicated one too, as it *doesn't* just incorporate "usual" BDSM, but lifestyle D/s.
Crash course: "Classic" BDSM functions in clearly negotiated scenes, while lifestyle D/s is a dynamic that becomes the "default" for how two individuals interact. It's not necessarily even sexual.
ATM, the only "negotiation" we have with Astarion is breaking up or killing him. Naturally, this is not what should be done between two real people. Lifestyle D/s needs immense dedication and communication to be healthy. It's not something you should ever jump into the way Tav/Durge does with Astarion. Consent is pre-negotiated. "Consent" in the way of "you can break up if you don't like it", would be seen as severely abusive behavior from a partner irl, on par with coercion. In game, there are writing limitations to explain all that, but please understand that each side has a basis to be rightfully upset and rightfully blasé.
