To comment on images we have posted, you must visit the blog and submit a response. Responses can be submitted anonymously, but I usually approve everything--unless it is clear spam.
If you don't see your response within 12 hours or so, consider resubmitting it. Occasionally when I approve responses on my smart phone, I click on the "delete" button as it is VERY close to the "approve" button. Once I hit that, I can't go and get the post back.