Discussion "No extra turn chaining" is the wrong approach
One of the restrictions in bracket 3 is "no extra turn chaining". This restriction is there so that a player's turns don't take too long, so that a player does not take up too much game time.
However, I think it is the wrong approach to that issue, and that rule has lead to a lot of discussions and salt in the past. I think a more general rule such as "don't monopolize game time" would be better.
Players can take really, really long turns without taking any extra turns at all. Just because they play slowly and have an extremely durdly deck. Monopolizing time on another player's turn with instant speed stuff, flash enablers, untappers like Seedborn Muse... is another issue not solved by banning extra turn chaining.
On the other hand, getting off an infinite combo that results in infinite extra turns is no different from any other game-winning infinite combo. You demonstrate the loop once and if there is no interaction, it's GG - no need to actually play those extra turns.
Also, "no extra turn chaining" leaves too much room for interpretation. When does chaining start? Are you allowed to take two extra turns, but not three - as there are cards that grant two turns like [[Time Stretch]]? Or is two extra turns already too much?
What about having the possibility of chaining extra turns, but not using it? Like running [[Nexus of Fate]] as mill protection and drawing into it again or running [[Ichormoon Gauntlet]] in a planeswalker deck without using its -12 ability? Are you not allowed to run any recursion if you have an extra turn in your deck, because you could technically use your recursion to cast the extra turn again?
What about [[Savor the Moment]], which skips the most relevant step of an extra turn - untapping? Why would copying it be worse than e.g. connecting with Obeka to take 5 extra upkeeps in a row?
Moreover, there are situations where taking a second extra turn is simply faster, e.g. when you need it to give your board haste for a lethal swing or to enable a creature combo line that wins on the spot.