It's Celebrate Bisexuality Day today, also called Bisexual Visibility Day -- a day to celebrate and promote recognition of those who are sexually attracted to people of more than one gender. The day exists because people with non-monosexual queer identities face unusual challenges in being recognized by both mainstream and queer cultures, yet visibility helps break down barriers and encourage acceptance.
In superhero comics, the problem of bisexual invisibility is as ingrained as anywhere; the medium struggles to acknowledge the existence of anything that didn't exist in The Honeymooners or The Andy Griffith Show, unless it's a space god, a shapeshifter, or a parasitic psychic monster. Having a character say, "I'm bisexual" is apparently more implausible than any of those things. There are signs that the industry is changing in this regard -- but slowly, and rather half-heartedly.