Sure, there are several standard places to attach text (at the Plant/Header level)
(based on how you want to share the data)
In MM03 and/or MM02, click on the "Additional data" icon.
The additional views (tabs) can attach documents and/or comments
(below is an example of the Basic data text containing dated comments pertaining to the material)
All the comments are at the Plant (Header) level.
Hope this helps.