'If someone not only does not say no or make any attempt to move away or stop things, they also participate, I can envisage how a person can reasonably think that they are consenting, ie agreeing, to do it.'
Not saying no does not mean that a person is willingly participating in an act.
If a mugger comes and takes my wallet, and I freeze, and let him do it - or possibly even hand it over, I am not participating, I am not consenting to giving him my wallet and he is stealing it - no-one would contest this, no-one would disbelieve the wallet-giver or think that the mugger could reasonably assume that the person wanted them to have it
The person with the penis is a person. A reasonable person would not put it where it is not wanted, and would not assume just because someone hasn't said no (when they are tired, drunk, and probably scared) that they have consent.
Not wanting a penis put inside you is not even slightly equivalent to not wanting to clean up cat sick BTW - the cat sick for example has no ability to stop being cat sick, it's not a person - unlike the person attached to the penis who can stop putting that penis anywhere, any time they like, and the person that penis is being put in who may be in very little position to stop.
I feel that this is going no-where - we have a complete disconnect on what is reasonable. I think it's reasonable to have active consent, you think that just by being there, consent has been given. I hope society starts seeing women as people and coming round to my definition of reasonable.