It was mentioned earlier that Battler’s moral compass is a bit off, and there’s some evidence of it at the start of EP4 when Ange drops her cup, disgusted at the scene of Rosa and Maria. Battler tells her, “This is where things start get interesting!”, which really seems to prove that he was enjoying the games and really just considered them fun games to play with Beato and clearly wasn’t ever taking the fact that the games could affect others (which thankfully, he does take that into consideration eventually). I’m not that good at putting such analysis into words, but on the Goats Rereading Seacats blog, they had a really good analysis of it, as a contrast between the two siblings.
But yeah, as a veteran of the series who joined in after EP5 came out and the anime was being released, what turned off a lot of people was that Answer of the Golden Witch interview Ryukishi had. It felt way too condescending, and while I don’t doubt some fans just wanted the answers handed to them, the majority of them just wanted to check if their things had been right, like at the end of most mystery novels where the answers are revealed to see if the reader got the answer right (like how at the end of And Then There Were None, all is revealed and things should generally click into place if they hadn’t already.) His attitude at least seems to have changed, since EP7 and EP8’s manga seems to have given a sort of checklist to see how things most likely occurred in the games, even if I think some of those answers (particularly EP3’s) felt cheap.
I might be reading into things, but there could be odd parallels (or maybe a different math term) in how Erika and Yasu are introduced to us. Erika’s introduced as being liked by everybody and charming the whole family with being a perfect and refined lady (which only seems to add onto the fact she’s a parody of Mary Sue self-inserts), while as Shannon and definitely Yasu, they don’t stand out too much (except to Battler, who wants to make everybody smile since it’s been a while since he last saw everyone) except if they make certain errors, and from there, they get scolded for their mistakes. They’re both extremely determined to do what they do (for Sayo, her determination that she’s a witch is what astounds Lambda in Lambda’s recollection TIP, and for Erika’s, it’s her assertion that she is the detective and WILL solve the mystery).