In case Larian won't address the Halsin/Shadowheart banter after swimming scene I want to give you the way I look at it that may help put your mind at ease.
I looked up this banter on youtube (idk if I can post links here, so I'll just give the name of the video and timestamp: Party banter [Romances] | Baldur's Gate 3, timestamp 3:51)
Halsins tone there doesn't seem suggestive, he just talks about it like going to a pool with his friends. And Shadowheart doesn't seem super excited, she just seems not confident enough in her swimming skills and genuinely worried that she'll need all the help she can get in case she starts drowning.
And as for the brothel scene I think that given the context, everything there can be seen as just "dirty talk" and shouldn't be taken too seriously.
Shadowheart not being upset about Mizora, how good are orgies for her mental health and if it makes sense for her character is a separate discussion, but it shouldn't ruin your experience with her romance.
