There is no rule requiring antiparticles to also have spin 1/2, nor that they in general be n+1/2 spin particles (fermions).
All lepton/quarks observed have half half-integer spin so there are no examples there. The SUSY sleptons/squarks would have anti-particles but integer spin if they exist, though. The W+/W- have spin 1 and are eachother's antiparticle. Z0 and the photon are their own anti particles, also spin 1. Gluons (spin 1) have anti-particles that are all another types of gluon. For composite particles, anti-deuterium and anti-helium both have integer spin.
For what anti-particles actually are, I suggest looking up both C and CP conjugation.
I agree, though as in a real market, the betting odds are quite sentiment driven. Maybe more so.
Many more people were betting "yes" than "no" (see oddschecker). This tended to skew the market towards a higher "yes" probability. At least one high-street bookie said the same thing. They said that they had their books setup effectively gave them a bet on "no".
This means the betting markets were optimistic on "yes". "Yes" was never that likely.
All lepton/quarks observed have half half-integer spin so there are no examples there. The SUSY sleptons/squarks would have anti-particles but integer spin if they exist, though. The W+/W- have spin 1 and are eachother's antiparticle. Z0 and the photon are their own anti particles, also spin 1. Gluons (spin 1) have anti-particles that are all another types of gluon. For composite particles, anti-deuterium and anti-helium both have integer spin.
For what anti-particles actually are, I suggest looking up both C and CP conjugation.