2022-10-07 : Although {T} acts in many ways like mana, it is not mana. An ability that triggers from a creature tapping to add mana wouldn’t trigger when you activate Sole Performer’s ability, for example.

2022-10-07 : Spending {T} allows you to activate the tap ability of a creature that’s already tapped. Normally, you couldn’t pay the cost of tapping the creature because it’s already tapped. With Sole Performer, you don’t have to worry about that. You have {T}!

2022-10-07 : Spending {T} rather than tapping the permanent doesn’t let you activate abilities of creatures that have “summoning sickness.” That is, if a creature’s ability has {T} in the cost, and it hasn’t been under your control since the beginning of your most recent turn, you can’t activate the ability (unless the creature has haste), even if you intend to spend {T} rather than tap the creature.

2022-10-07 : You can’t spend {T} to have a creature attack without tapping. You also can’t use it to pay the cost of an ability that taps a creature without using the {T} symbol. For example, you can’t activate an ability that says “Tap an untapped creature you control: [Do something]” with {T}.

2022-10-07 : You lose unused {T} as steps and phases end, at the same time you lose unspent mana.