All these algorithms arent going to help if user A changes a headline from Arial to Helvetica while user B changes it to Helvetica Neue.

There is no way to tell which of the changes should win.

That's why most applications decided to require users be online for edits. when you have to be online, the chance of simultaneous edits becomes so small that you can just show an error message instead of trying to merge.

The online requirement also ensures that you are notified of conflicts immediately, which is vastly preferable to users. Nothing worse than working on a document for hours and discovering someone else also worked on the same document and now you have two edited copies that someone needs to consolidate.

That's the reason why offline first is becoming increasingly unpopular.