Same problem years since original post:
1) Edit note in first browser
2) Open note in second browser on another computer and edit
3) Come back to first browser that's showing the note and make a change (forgetting to refresh, I switch to and from the browser Evernote tab regularly)
4) First edit made in first browser is lost without warning
FAIL!!! Really this is still broken... This is basic version and conflict management as a previous user said!