The flaw in your logic is you assume the only way they can get personally identifiable information from you is if you provide it yourself. The very fact you use Gab on the same device as other accounts means they can associate your Gab profile with *every other service* you use online. Unless you browse Gab exclusively on a black box machine of some kind (literally no way the device can be traced back to any thing, place, or person even remotely related to you), they can figure out that your Gab profile is associated with your Poal, Facebook, Gmail, Bank account, etc. One of the ways they do this is via browser fingerprinting. As well, HTML5's canvas via "invisible" tracking pixles.