Especially in the Mechanics section, where the thread containing the exact information you need might be very old. Making comments to those type of old threads - maybe asking for more information or clarification is fine I would think. I'm not a fan of deleting any history.
I just asked Ibobbi again this morning where the site stood on bringing back the original post date beside the OP's name under the thread title. That would flag old threads without having to open it up. That was here before the last (upgrade ?)