It would be fantastic if when converting item types (in this instance, from a project to a task type) that all comments/conversation from the original item were also brought into the new item. There is often essential communication that is a part of that feed before it's converted that then is either lost or had to be manually moved to the new item. The same goes for any attachment comments.
Ideally, maybe when converting from one type to another, there would be a selection box of what data needs to come over, much like when duplicating an item.
For example - that item conversion selection tool could ask if Custom Fields, Assignees, Comments, attachments, etc need to be a part of the migration. In many instances, I would guess they do.
