When looking at an asset, under the action menu you can attach various things, one of which is a document.
What I'd like to suggest is the addition of 'Add Note'.
This would use the exact same storage method, display method, etc. as attaching a document, but instead of opening up a dialogue asking for the file to upload it would open up a dialogue containing a rich text editor with 'Attach / Cancel' buttons.
On attach it would just create a file in whatever the internal structure of a 'Solution' is on the server which would be treated exactly the same as if you'd uploaded a file.
The only difference being that when you click the link to the file in the attachments list it would open in the browser instead of kicking off a download.
If this has already been suggested could you point me at it so that I can give it a 'me too!' please?