All their comments are dead

I don't get it. How do you know that GP is shadowbanned? The post looks just like a normal post to me; I'm not even sure what it means for it to be dead.

if part of the way the shadowban works is that the banee isn't alerted, why are you alerting them which works against "the system"?

Because "the system" might have made a mistake. And even if the shadowban was warranted at some time, the poster might have improved their conduct in the meantime and should be given another chance.

Usually, when I see a reasonable but dead comment, I vouch for it. If the commenter is shadowbanned and their other most recent comments are also reasonable and civil, I (sometimes) alert them to their status.