Your sync and merge has long been broken, and I hope to provide you enough detail to get it fixed here. All the below should be reproducible, let me know if you find otherwise.
It starts simple. Create a note in Evernote webview. List some fruits. If you’re anything like me, you probably make a couple lists like this per day. All seems well. Later that day, you remember this list, and have a burning need to add “Starfruit” to it. All looks well?
But things are not so well, because when we return to the webview, there’s some bad news awaiting:
^– Now two notes, instead of one
That’s right, my fruit list has split itself in two lists with edits from desktop and mobile. Similar problems persist as I try to use the document.
Unless one is fastidious enough to sync every note when finished, and then manually sync when resuming on another platform, you are liable (at rate inversely proportional to speed of your internet connection) to soon find yourself with something like this:
Every time I switch devices, I must remember “ensure save,” then pre-sync on the new device (and remember to confirm sync finished). Granted, there are a number of trigger points for syncs, but it’s impossible to be sure which, if any, have triggered/completed. One too-fast move, and I’m back in the ghetto of Mergetown.
I usually don’t even know I’ve been losing list items (to duplicated versions), until I notice the note lags in load/save time. And then I realize there are 10 copies of the list in my note, below the (already long) version I was treating as the “real list.”
I sympathize that getting sync to work reliably across disparate platforms is a hard problem . So why not, instead of fully fixing the sync, just spend a few days fixing the merge?
If you could automatically add new lines to both documents without creating duplicate copies, that would be a good start. If you kept the note differences in the area they were found (not bottom of document), that would help. Source control tools have spent 20+ years building great systems to merge two documents. You can probably crib most of your implementation from a plugin/library in that domain? Or at least mark “duplicate documents” so I know I’ll need to hand merge them?
Thanks for considering these improvements. I take the time to write this because I still believe you’re the best solution in your space. If you could just address this fundamental stuff, I’d reap benefits greater than the (sizeable) time it took to create this report.
 Lists featuring fruits.
 Albeit the hard problem you ostensibly built your business to solve