If you use the PM conversation to take notes, how will you find the note you need later?
For less than 100 notes, you could just scroll up/down in a linear list of notes.
For more than that, you need some kind of tree structure, or search feature in the note app.
It reminds me of an old function that I liked but lost. If I remember right, it came from Google Labs. It create indexes of the content of all the files on my disk thus permitting fast full-text search. Then I could make searches and specify if I want local- files/cloud-files/emails/web-pages to be included in the same search. If I had been active on PF at that time, I could have included a custom search of my own posts on PF in the same search. It even included comments in program source code, and static text data in executable files. It could also index offline storage like floppy disks or backup tapes to be included in the search; only the index was required to be online, not the actual files.
The results were presented in rank order, and all the options and qualifiers of the Google search engine could be used.
That had the advantage of searching without the need know which app I used, or which location I stored it to create and store the information. But alas, like many other things, that Google feature disappeared.