Let's say you make a comment on a Google+ post and someone comments on the post after you. You'll receive notifications with links back to the post. Even if you have disabled notifications, you can still find the post you commented on by navigating to https://plus.google.com/notifications/otherposts via Notifications -> More -> Posts by others.
If you make a comment on a post and no one comments after you, however, you may well have trouble ever finding that post again. You'll receive no notifications (there's really nothing to notify you about), and I'm not aware of any URL you can visit to see those comments you've made when no one has yet commented after you. Is there such a URL?
Sorry for all the emphasis, but I've already asked about this on the google-plus-discuss list, and multiple people have mentioned notifications, which are no help when no one comments after you.
I really think this deserves an entry on the Google+ Known Issues page. I'm less inclined to put any thought into comments if I know I may never see them again.