I have found out that one of the materia shop in Junon (discs 2 and 3 post-highwind), has been changed from the original game due to the reunion mod... now selling Magic Plus, Withdraw, Revive, All and some others instead of the orginial materia set (Sense, Seal, Restore, Heal and Revive). Has this been changed on purpose? It's weird but if done so, you've got rid of the only way to get Seal on disc 3 so you may want to change it in the future.
Thanks!