I’d rather resurrect the old smoking thread every time I attempt to quit smoking than starting up a new one, its better to resurrect rather than fill the space up with similar or duplicates.
The warning makes sense because I know from other forums that a typical newbie thing to do is search the forum based on topic, and respond to the most interesting threads, often thinking they are jumping into an active discussion when in fact the topic has either died years ago, or there have been several more recent threads on the same topic, but perhaps with less catchy titles.
The warning lets you know what you are doing, and you can reassess if it is not what you intended.