My two cents.
I think it is OK to jump in and out of the line as you see what you want. I do not butt in if people are waiting for sliced meat, omelets, crepes, stuff like that. Many buffet lines seem to be multi-directional. I am tall. so I can see what I want, am able to walk fast etc. Some people seem to have trouble making food choice decisions and then slowly stroll to the next section. Enter the buffet on a mission, get what you want, sit down, eat, repeat!