That makes no sense
That makes no sense, and I say that as someone who has replaced more than my fair share of keycaps on MBPs.
The plastic part of the key is just for show, what actually makes up the key is a little pressure plate/sensor that sits under a rubber plunger which is what causes the key to pop back up when you press it. Then there's a little scissor mechanism that helps distribute the force of your pressing on the key a bit more evenly. On the shift key there is a metal bar that is purely for holding the keycap in place. I know this, because I have had several MBPs in where the rubber plunger had been broken off, but I could still get the key to function by tapping my finger on the pressure plate. I also know that according to Apple's KB article regarding replacing keycaps, if that rubber plunger is missing, they say that a new top case is required. Presumably if you still had the plunger you could glue it back down, but odds are you'd end up making the situation even worse.
The above post would only apply in situations where there was some sort of mechanical issue with the key such as sticking, not where it was unresponsive to key presses. Add to that Bob's mention of the poster spamming, and the best case scenario I can come up with is one of general gross incompetence.
I would myself suggest that the above post, and the associated replies, be removed. The information is WAY off base, and then there's the spamming aspect of it as well.