During the phase of development on one of our backlog items it often occurs that we need to re-estimate our stories/tasks as new facts impacting the effort of the task or requirements change.

This means changing the story points of the item. Whenever we do this, however, we lose the previous story point estimation and thus the ability to track how story points have changed and how our sprint velocity was affected.

I believe Jira already offers estimation-change history for time estimates. Since we would prefer to stick to story point estimates, I think it would be very useful to add such a tracking feature there as well.