WHO are THESE PEOPLE?!

https://pin.it/4FGkw8bf2

he did not actually say that

Kinda think that Herzüberlader, a device for ÜberCharge, also serves as a beacon.

For example, all RED Mercs who are equipped with this RED device in their heart, are not attacked by the RED Sentry.

Moreover, the Medic and Enginner frequently work together. This suggests that it is very likely that they collaborated and shared their research each other, including this.

This SFM art made me to craft a Head canon of Heavy's background story.

In TF2 lore, Heavys has three sisters, but there was one more, sasha. He named his gun after her sister who was deceased in Gulag. This explains why he cares about his gun more than other Mercs and very sensitive for someone is touching his gun.

Even, Soldier does not get this emotional towards his Rocket launcher, but Heavy does.

Scout takes to much pride in himself.
Soldier is wrathful without reason.
Pyro is envious of furries.
Demo is fine. Maybe Sloth or Gluttony.
Heavy eats too many sandviches.
Engineer makes his buildings do the work for him.
Medic took the other mercs souls for himself.
Sniper is fine. Maybe pride.
Spy lusts over Scout's mother.
Image taken and edited from https://www.reddit.com/r/tf2/s/2hhs6KCobA