I’ve been waiting for someone to point that out. It was clearly pedant bait.
Guilty as charged –
Ditto.
“Righten” actually is; it means “to set right,” or “to restore to a normal or upright position.”
Not so much for “leften,” however.
You’re right! Thanks for setting me right!
You have been rightened. 
Alrighty, then!
NM, ninja’d
Gunter glieben glauchen globen leften loosen.
You are doing that backwards. Stop it right now. @TriPolar is already confused. A third choice may send him over the edge.
Left to loosen, right to tight.
Totally agree; one can’t loosen something until one tightens it first.
Except that is nonsense, right? A screw or bolt has an axis of rotation around which you can turn it clockwise or anti-clockwise. There is no way to turn something to the right or left.
I can turn it towards my right or my left. That’s what the saying is about, however phrased; and most people find it quite useful.
(A problem does arise when the nut is upside down from the person. I mostly deal with it by imagining being upside down myself.)
Lefty Righty; Loosey Tighty.
You can turn the top towards your right or left, but you will automatically be turning the bottom the other direction.
Not really. I speculated that it has to do with the “right-hand rule”. That rule does not say that you turn anything to the right or left, however. It means that if you have a right-handed coordinate system (or screw), the positive orientation is as illustrated:
If you turn the bolt in the direction indicated by the circular arrow (I would not call that “right” or “left”, or even “clockwise”), it helixes/advances in the direction of the straight arrow.
So what?
One can’t tighten something unless it is already loose.
Sure you can. You can make something tighter. It can be more tight. It can be tightened more. However, it can’t be more tighty or tightied more, or tightier because those aren’t words. It’s difficult to type this post because the spell checker keeps changing them.