Well, I assume I'm one of these culprits, so please don't beat around the bush. I'll just respond directly.
DC always used to automatically re-size photos rather than show the whole image full size. I don't know when that changed, but I suspect it's just a forum setting that was inadvertently turned off during a recent maintenance update. Maybe one of the admins can turn it back on again.
I don't like uploading photos directly to DC because that takes up server hard drive space. Instead I prefer to use my regular photo site (my phone automatically uploads images to there) and just linking to the photo.
And Addie... what in the heck are you talking about when you say 4x6? 4x6 what... inches... feet... cubits? FYI, computer images are measured in PIXELS, and pixel sizes vary from one device to another.