Rabbits have an etiquette when being greeted, and can go into a strop if you don’t do it right. It can be likened to a handshake, with rabbits just as likely as humans to give pathetic, limp versions or forceful ones.
To say “hello” to a bunny, you give them a gentle ‘punch’ on the nose. They generally bump noses, but will bump anything of yours if offered, such as feet, fists, shoes, noses and knees. I have offered both feet and fists to Pixel, who greeted all four quite vigorously.
Nybble has always been pathetic at this, and gives a sort of sniff-touch-backaway bump, whilst Pixel puts a lot of force and effort into his greetings, often double bumping in quick succession.
Rabbits can get upset at you if you don’t say hello, so if you ever pass your rabbit or haven’t said hello for a while, offer your fist/foot. They will either greet it, or sniff it and hop off (possibly in horror if offering smelly feet) wondering why on earth you want to say hello again. Stupid Humans!