I think you're talking about the Similar Threads that can be seen when you make a new thread, as well as down below the thread. These are automatically generated by a program. Sometimes the program does well....and sometimes it kind of stinks.
In the case of this thread, the automatically generated "similar threads" are:
Extreme Saying
Playing "devil's advocate" on the mortgage debt issue.
help me break up with my lawnmower
Am I ready to make the leap?
predators/humans in permaculture
And, you're right, these really don't seem to have anything to do with your post. The program kind of failed here. Though, I admit, I can't think of a thread off the top of my head that would fit better. So, I can't really blame the program.
But, thankfully, we can (though we rarely have the time to) manually change the similar threads to ones we think are a lot more relevant. Generally, this only happens if a moderator is interested/knowledgeable about the subject and has a spare moment. Frankly that happens a lot more threads about
gardening or building, etc.
But, if you have a thread and see the Similar Threads are totally unrelated, you could click the "report button" and ask a moderator nicely to add some of those to the similar threads. Someone might just have time to do it, especially since you did the footwork!
I hope this helps explain things a bit!