For the simple case of electron-positron annihilation, they transform into high-energy photons, whose total energy is equal to the total mass-energy of the electron and positron. See: https://en.wikipedia.org/wiki/Electron–positron_annihilation

According to Crusader Kings, the Norse

People figured out the performance issues with Starfield when it was first announced: the Bethesda logo

“You didn’t hear that”

that puts a barrier on new users and enforces echo chambers

Only if trust starts at 0. A system where trust started high enough to not filter out posts and comments would avoid that issue.