There are different level of thread hijacking IMO>
If a guys answers an engine question and the next post is, "BTW how did you tire thing work out?" thats still pretty benign.
But an other example is : One guys posts "Look this is a way way to do this and BTW I have this FS in BST" and the next guy goes "this sucks we really should do it this way you always post BS and BWT folks look at my BST instead".Then thats an example of more problematic hijacking.
Fred...