When having multiple notes in a timeline (On the agenda for example), the end and the beginning of a note are sometimes hard to separate.
Perhaps this is wanted, I however get confused by not having a clear border between notes. Having that, would be great.
We do include quite a lot of whitespace there, and the title is larger than the rest of the text. The buttons top and bottom also help delineate somewhat.
We originally did design the app with full box borders, but it was way to busy and cluttered.
If it is very important to you, have you thought about adding a horizontal line at the bottom of each note. You could perhaps even make template with a line in it, and always make new notes with that template.