User jAm-0 has issues getting into and out of his phone's bootloader. He attributes this to the bootloader being corrupt and wants to replace it.
User return.of.octobot provides instructions to allow reflashing the bootloader. One of the steps is to run fastboot flashing unlock_critical, which allows the bootloader to be overwritten.
Overwriting the bootloader is the only way to hard brick most devices, and fastboot flashing unlock_critical tells Android you don't care and are willing to take the risk. Hard bricking makes a device unfixable on the software level.
jAm-0 has another question and receives responses from return.of.octobot and another user, nrage23. Again, no disclaimers are given and the word "brick" isn't even brought up.
jAm-0 hard bricks their phone.
I mean yeah disclaiming risks is important, but googling what you're messing with is as important.
If I'm messing with a core component of something I'll google until I'm 100% certain of the effect of what I'm about to do.
If someone were to tell me to replace some part in the engine of my car, I'm for sure gonna google everything about that even if I trust that person completely before I even pop the hood of my car.