This thread caught my eye. I have been playing with this feature for hours, and I have fully figured it out.
To understand how Notes work in Gmail, one must focus on the fact that Gmail uses labels instead of folders. Apple Mail will treat these labels as if they were folders.
You're getting multiple copies of your Notes because Gmail archives your mail by default rather than deleting it. When you create a note in Apple Mail and save it to Gmail, Gmail will apply a label called "Notes", but only if you have the option to "save Notes in inbox" unchecked. Otherwise, these multiple note copies will appear in your inbox.
Why? Because every time you update your note in the inbox via Apple Mail, Gmail treats it as a reply to a conversation, and creates a stack of cards. This stack of cards will be tagged with the "Inbox" label. In Gmail, the stack will appear as a conversation with yourself. For instance, if you updated your Note six times, your note will appear in Gmail's web interface inbox with the subject followed by a (6).
Why the multiple copies in Apple Mail? The reason is because Apple Mail treats the stack of replies as individual messages. And because you saved the note in the inbox that maps to your Gmail account, you're going to get every update to the note you made bounced back to you.
On top of that, Gmail will label the conversation with the "All Mail" label. Remember how labels show up as folders in Apple Mail? For every label that's appended to a conversation in Gmail, Apple Mail will save a separate copy of each part of the conversation as individual messages, in each folder corresponding to a label. Using the above model, you will see six separate notes as individual messages in your "All Mail" folder on Apple Mail.
How do you reduce all this clutter? The best thing to do is not having notes show up in your inbox, but rather under the "Reminders" drop down arrow. I unchecked the option in Preferences > Accounts for saving notes to the inbox. Still, if I click "Notes" under the "Reminders" arrow, I'm going to see all the notes on all of my IMAP email accounts, and the local notes on my mac. Because of this, I'll see multiple copies of the same note, each gradually including more text to the body of the note, listed as being in my "All Mail" folder.
Just selecting the "Notes" subcategory for my gmail account, I'll see only one copy of each note; the latest version that I modified.
What's more annoying, is that as soon as you make a note, before you get the chance to name it, Apple Mail will send it to Gmail with the subject "New Note". In Gmail, this will create a stacked conversation for each note you make under the subject "New Note". Depending on how many notes you make, for example, it may appear in Gmail as a conversation called "New Note (83)", but it'll appear in your "All Mail" folder on Apple Mail as 83 separate notes called "New Note"!
So, you can reduce the amount of multiple copies you see by unchecking the "store notes in inbox" option under the Preferences > Accounts pane. This way, Gmail on the server side won't apply the label "Inbox" to your notes, and likewise your notes won't appear in Apple Mail's inbox. Rather, Gmail applies a label called "Notes" that skips the inbox and places the archived note conversation in "All Mail". The "Reminders" > "Notes" > "Your Gmail Account" drop down item in the left hand pane of Apple Mail is simply the mapping of Gmail's "Notes" label to an Apple Mail folder. This folder will only display the latest editing of each of your individual notes stored on Gmail.
I know - it's confusing. Hope this helps.
