Our open zones are conducted on open roads among recreational cyclists. We are not racing for anything; the open zones are for fitness and recreation; thus, our key issue is safety.
Safety is best served if we mostly maintain a relatively tight 2-abreast formation throughout the open zones with one advancing line and one receding line (usually right advancing, but depends on the wind).
We should keep enough space to the LEFT of BOTH lines for riders to drop back after pulling so that cyclist does NOT have to hug the yellow line (again, safety for cars passing, etc.).
Early in zones, when the pack is stretched out, it seems fair that an attack up the far left is OK, but still, that likely should be accompanied by some verbal warning of “on your left” and the ability to maintain the attack.
Blasting by on the far left up a hill and then coming to a wobbly crawl as a fast pack approaches from behind is both bad form and dangerous.
We are all safest when we can all count on each’s other’s predictable behavior on the bicycle. If you want to be the one person who does as you please (disregarding other’s safety), a solo ride may be best for you.
Also bad form is not contributing to the pulling so you can do your blasting up the left and off the front. If you want/need a good work out, take hard pulls in the open zones.
Never advance over the yellow line. If you get blocked in, such is life. Open zones are for recreation, not the World Championships.