The photo galleries can be found by clicking on "Galleries" up above (near the top of the page but under the StampTV banner.
Or did you mean, how do people know if you commented on their photo? It will also put the comment on their page here at GKD, but what I usually do is click the "Follow" button under my card so that it sends me an email every time someone comments and I know to come see what they say.
Members here are so kind and generous with comments! I agree it is fun to get feedback on your posted cards! Hope that helps!