Re-Raising An Incomplete All-In Bet, What's the Rule?

X = allin for 500 suddenly gives Player A again the right to raise?

Is this representation accurate? Anyway, what's the reasoning behind an incomplete raise? Seems so random given these scenarios.

It doesn't "suddenly" give A the right to raise. A has the right to raise as soon as B made it 300. C can't do anything to undo that right.

The reasoning is simple. To be a complete raise, a raise has to be at least as much as the previous bet or raise. An all in for less than a full amount is an incomplete (or "action only") raise which any player who is not already facing a full raise can only call or fold to. Multiple all ins for less can combine to form a complete raise (if they do).

It changes the total amount of the min-raise though, doesn't it?

If X is all-in for 310, the min raise is still 200, but put on top of the 310, so it would total to 510. Is this correct?

Had a situation come up like this one time in FL.

I asked the dealer "can i raise?" - was my first time in the room.

Dealer said "i can't tell you"

Me - "so i have to raise and you say if it's legal or not?"

Her - "yes"

Bad customer service imo I would stiff this dealer for the next hand or two. I don’t see why they can’t tell you you’re options unless there’s some specific house rule against it.

Yes that is correct. If A bets 100, B raises to 300 (raise amount of 200), C goes all in for 310 (action only), then the next player who wants to raise has to raise the current action (310) by the current min raise amount (200) to be a full raise, or a raise to at least 310+200=510.

Sometimes that is exactly a bad room policy. Sometimes it's a dealer (mis)construing the OPTAH rule.

IMO as long as a player waits to ask until the action is on them, it is a question that can be answered, as are any rule-specific questions (particularly ones that are often different room by room, which this one is not really). A player is entitled to know the rules of the room.

Note that some devious players can use leading questions like this to try to influence the action of other players, i.e. they might ask if they can raise, not because they want to do so themselves, strategically, right now, but because they want to plant the seeds of this possibility in the brain of some other player (most likely because it benefits them, e.g. if a player right behind them could raise all in and it would be enough for this player to then trap any intervening callers with a reraise). There isn't much you can do in the moment, and this is such a rare and unlikely event in the first place, but if you have players who bend the rules like this you give them a warning after the fact and then give them time off if they continue to abuse it, just like with many other rules and angles.

Also note that some experienced dealers disagree with the above, and come down on the side of answering it being a OPTAH violation. I don't agree with them, but it's not a firmly settled point.

The dealer was clearly female.

MP can raise when it comes back to him because his $5 was already raised to $25. That's a raise and reopens the betting for him, no further action can CLOSE this already opened betting right. However if everyone now flat the $27, then BTN will not be facing a more-than-minimum raise and can either fold for $2 more or call $2 more, closing the action.

Yeah, I legit can't fathom how anyone can think that MP could raise once BTN raises, but then somehow that right would go away due to anything an intervening player does.