From one side it was nice to put infinite possibility of adding comment to a comment, but at certain moment, the thread tree looks like in the printscreen below. I believe, some reasonable restriction should be applied anyhow.
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I have proposed compromise solution here: https://answers.sap.com/questions/106239/flat-structure-vs-threaded-structure-please-let-in.html
There is also an idea on this which I up-voted recently
Flat list is an alternative solution but in order to have a readable tree view - the tabulation has to be stopped after some column length is reached.
Even in archive this method is working! Sample of the long tree: https://archive.sap.com/discussions/thread/3508344