It is a grave accent. Something which was and still largely is of little use to many that grew up in United States knowing only English. So, such users abused a

It is a grave accent. Something which was and still largely is of little use to many that grew up in United States knowing only English. So, such users abused and re-purposed it as a "backtick", which feels like an unfortunate decay due to ignorance. But such things continually happen.