>>>How about adding a "Reply in a new thread" button next to the Reply button at the bottom of a message? This will offer an quick option when you want to respond with a message that is off-topic, without polluting the current thread.
>>>
>>>The "View previous message" and tree hierarchy buttons would still show the new message as part of the old thread structure, but you would not see the new thread from the original thread.
>>>
>>>Hope I was clear enough...
>>
>>Or name it 'Reply in a subthread'. The 'new' thread remains in the thread's tree, but its title will distinguish it from the orignal thread.
>
>I like the original idea better. In other words, we may have a new button when you press reply to start a new thread with a different title but yet preserving the original message you're replying too. The link to the original thread may be inserted into the top of the message.

Now you've hit on something. I think that's a terrific idea. Kudos.