I'm a pretty 50/50 bisexual female and a vast majority of my PCs have been bisexual females. I just can't call it pansexual, I'm sorry, maybe I'm just too old but I accept an all-inclusive meaning and like how @Pandora explained it - attraction is about the person, not their genitalia, for me.
The one time I ever made a serious attempt to play a male PC, it came from the idea that maybe by doing so I could buy myself a break, some space, something. At the time, playing my female PC was claustrophobic and suffocating because of the way people were acting around her, to her, and about her, but seemingly never with her, if that makes any sense at all.
Within five minutes of stepping onto the grid, a pair of female PCs tried to waylay my middle-aged, wedding-ringed man into the forest with a really overdone sexy scantily clad damsels in distress scene that just... ugh. Within a week, multiple female PCs mine had interacted with in the same fashion as male PCs had staked 'claims' to my guy and were doing the same awful stuff to each other I watched them do to each other from my female PC. It was horrible. I'd thought it was bad to observe as a female, but it was a hundred times worse when it was AT me.
The apparently straight male PCs were actually really pleasant to him, as I saw no overt or possibly passive-aggressive signs of jealousy or the weird alpha posturing stuff some guys do in these games, and they'd always emote back at me, have conversations with me, buy rounds, roleplay poker, billiards, whatever... the whole building blocks to deeper IC trust and involvement.
I never met any gay or openly bisexual males that I'm aware of, i.e. no males ever made obvious passes or showed any iota of interest in him other than friendly dude joe bro type stuff. This was awesome. I got to see better writing and roleplay from quite a few of these guys than I ever got to see on any female PC I'd interacted with them on, which... actually, kind of sucked, in hindsight, but was really fun at the time.
Another time I rolled in an openly bisexual guy to help another player I respected try to get an organization off the ground and... well, that very same person more or less ignored me andmy once he'd figured it out, and I ended up shelving the PC over it. Never hit on him. Never came up ICly or OOCly in any conversations, but the mere act of making and playing a man who wasn't particularly traditionally masculine and with variable sexuality pretty much killed a friendship for me. That was pretty wrenching.
I never really figured out how to parse or process this. I still haven't. I guess this post is stupid long, but the intersectionality/mu*sectionality threads and debates really got me thinking about my experiences in this regard and since I'm following the threads I figured I'd share.