Let people mark individual trades as invalid

[speezepearson]

User story: I, a user, see a prediction that I disagree with, and I place a bet against it. Wait, shoot-- I misread the prediction, I actually agree with it, I want to retract my bet.

Current behavior: I'm out of luck! I need to, like, call my friend who owns the prediction, and tell them to ignore my stake; and even then, my bet counts against their maximum exposure forever.

Desired: there's some button that lets me retract my bet.

[dreeves]

Another (true) user story: User places bet and, through UI confusion and/or user confusion, makes like 3 different versions of it. https://www.biatob.com/p/10530152680375280431

[speezepearson]

Thinking out loud: open question: is it "dishonest" for somebody to retract their bet in response to material new information that wasn't available when [the predictor was crafting their odds / the challenger committed to the bet]? I think so. So, how does the UI discourage this?

The simplest thing I can think of is to have a required checkbox labeled "I promise that I'm not changing my bet in response to new information, I just made the bet by mistake." But that sentence is so long, basically War and Peace–length -- would anybody actually read it?

[speezepearson]

Thinking out loud: as long as we're talking about making bets mutable (at the very least adding a "retracted" flag), maybe it would be simpler to conceptualize a prediction as having only one bet per challenger, rather than multiple bets whose stakes stack.

Example: suppose I make a prediction at 2:1 odds, and you bet $20 against my $40, then you sleep on it, grow even more confident, and wish you had bet $100 instead. \ Currently, you would reach your desired stakes by making another bet, your $80 against my $160. \ In the alternative model, you would alter your existing bet, changing it from $20:$40 to $100:$200.

(I would, of course, leave an audit trail, so that the bet's revision history is visible to either party if they care to go digging.)

Advantages:

• Seems simpler. Easier to understand what you're on the hook for.

Disadvantages:

• Takes work to change, obviously.

Open questions:

• How does this interact with retraction? (a) One could think of "retracting a bet" as "changing the stake to $0" -- but that feels a little bit shoehorned. (b) There's already a flag on the Trade that says whether it's "queued" or "active"; I could add another enum value for "retracted."

[dreeves]

Ideally-ideally, your bet starts a prediction market and anyone can always put in money in order to change the market probability at any time! Like a Hanson log market scoring rule mechanism. It's so freaking beautiful.

Back in current reality, I would say no altering a bet once someone has taken the other side of it. But with a nice audit trail it could be ok I guess? Altering bets before anyone has taken the other side seems very kosher.