As I read this, Buffer doesn't pay remote employees less. Rather, you're payed more if you work from expensive cities (eg. Hong Kong), than if you work from cheaper cities (eg. Bucharest)
I understand the cost saving benefit from an employer's perspective, but since that's not me, I've chosen my side.
Also, from a employees perspective if you feel you're getting a lower wage than someone who is of less value to the company, you can always try and renegotiate your salary.