> but does Reddit even allow photos anywhere besides thumbnails?

How is that even relevant? Images cost in bandwidth, not in computing power.

> Does Reddit find things only specific to your account

Uh yes, on every single submission and comments. The admins clearly stated that what used the most resources was the voting system. As well as every single user (whether you marked them as friends) and the list of links itself, which is extracted from the user's own list of reddits.

There is barely anything on a logged in user's page which isn't at least in part specific to that user's account.

> I could really go on for a long time

No, I don't think so, you've been 0/everything so far, it's time to stop.