I don't have a problem with changing node titles in followups, but I'd prefer that the change include the previous title (eg "Details of.. " or "Details (was: Re: .. )"..
in reply to Q re nodes' subjects
The reason for this lies in how the simple search works (the box at the top of the page), it searches in node/reply titles only.. Thus if you remove all the key words, that node won't show up in a search result. Yes, the root node will, but people may not click on search results that appear to have no answers/followups..
So yes, while nodes/replies are kept together via the thread mechanism, the search methods (both of them), treat each node and reply individually.. So please keep meaningful titles, and not one-word ones..