I think we should be able to 'delete' the food that our pet has eaten. Like for example my pet is mainly a vegetarian so that if I accidentally gave something not veggi to my pet, I can delete it. It'd help for a good pet profile display so when people click on there they will see a kind of TC but for food that the pet eats.
It can also help that if at some point I gave my pet something and then I decide that my pet should have not eaten that, I can just delete. I mean, you can not like throw back what you already ate yesterday but it could be nice not to be bounded to our past :) tehe
[edit] Deleting would imply not getting your item back, of course. That'd be a hell of a mess.

I disagree with this. Where do you draw the line if people then suggest removing items from collections, unsticking stickers, "unreading" books, etc?

Meh, I disagree. The point is that as there is an achievement for having eaten a lot of different foods, food is basically a collection. You can't take anything out of any other collection either, so why should you be able to do it with food? The real life approach sounds weird, too: would you have your pet digest backwards and spit it back out?
Plus, the food a pet has eaten is rarely used in the fashion the TC is. People usually just collect the specific foods for their pets and display them in their TCs. If you really plan to link people to the food a specific pet has eaten, then feeding that pet should be carefully planned, just as you would do with a TC; so in the end you can use a TC anyway and I see no need for someone to use the "foods eaten" page.
I dont agree with this one. If you turn vegetarian from omnivore, you certainly have eaten some animals in the past, so yes those are "foods eaten" and your new dining philosophy will not change that past-reality in any way. Also, vegan/vegetarian friends of mine tell stories of having accidentally eaten meat not realizing it.
If this is in service to a Petpage, I think it would be fun if you were to write those meats off as unfortunate past/hilarious mistakes, and then write your pet's story around that.
I accidentally fed my gourmand something that he as a character is allergic to. As much as it annoys me that I did that, I now have a little message in the notes section of my sidebar that says "-Mental Note: Don't feed Knives Anything with Strawberries in it" to help me remember.
It's already been said, we can't remove things from other collections and the food for the Gourmand Achievement is just as much as a collection as those. It's just labeled different.
