been puzzling for a while about Tyrion's comment: "in former days, she had run Lord Renly's household in the city, which had given her a deal of practice at being blind, deaf, and mute." This framing of Renly is much more scandalous than the way other characters who know about his sexual preferences refer to it, why?
I think it's hard to measure "scandalousness" of comments compared to what other characters say. Stannis's comment about Margaery being likely to die a virgin in Renly's bed is snide; Jaime's threat to shove Loras's sword somewhere Renly never found is crude. There's homophobia underlying all of it.
Now, it isn't clear from this quote whether Renly's seeing multiple partners, Loras repeatedly, or casual partners/shorter relationships prior to a longer-term relationship with Loras. But that's kind of a moot point. The homophobia here is in the fact that Renly's same-sex relationship, any same-sex sexual relationship, is inherently scandalous to the people of Westeros in a way that heterosexual sexual relationships aren't. If these were women going in and out of Renly's house and spending time there, nobody would bat an eye. A servant wouldn't need practice at being blind, deaf, and mute.
And that's all taking place in the capital of Westeros while Renly's at court - not as dangerous as Cersei and Jaime's relationship, but certainly not risk-free for Renly's political career either. The scandal potential is a click or two above normal, even if the reason for that is fundamentally homophobic.