I'm not going to get sucked into this vortex of a thread. Let me say thought that it is a very common practice to clone or double tracks by copying a track. This is different yet similar to putting more than one mic on a source or recording a part played twice. Yes there is an increase in summing volume with all of these.
In cloning tracks you can treat each track differently (whether it's EQ, Dynamics, panning, effects, etc) and then blend them to achieve a different sound result. In the example of the kick drum, treat one kick track like it actually was a mic placed closer to the beater end boost/cut EQ bands to get more of the click effect and the second track cut/boost to achieve the boomier sound of a mic placed farther in front of the kick. Then blend to taste. It can a completely different result than just boosting/cutting the same frequencies in just one track. Try it yourself and see.
Another similar result is when you have track send to a buss. You blend the buss level with the track level for a different sound or result.
A cool trick you can try with vocals, drums, etc is to clone lets say a vocal track. Treat one track however you want. With the second, compress the hell out of it and then blend it with the other track. This is a great technique for getting some thing to stand out more in a mix. Maybe put reverb on one but not the other.
There are limitless tricks you can do cloning a track, treating each track seperately and then blending them to get a totally different sound. The sky and your CPU are the limits. To the poster saying it's a waste of CPU .... there's ways/workarounds to freeup CPU, try bouncing tracks or archiving.
Here's an article that supports the whole notion of what's being argued and discussed here:
http://www.recordinginstitute.com/R2KREQ/excomp.htm
Remember, in recording there are no rules and if it sounds good ...... it is good! Keep your mind open to new possibilities.
Sometimes when I construct a drum track from drum loops to get it to sound bigger and have more dimension I will typically have the main track and use track EQ and compression to get a great sound by itself and then a reverb send (and then maybe another send which I EQ and Compress on the buss with different plugins than the first track) and then I'll make 3 clones of this track and......
using typically a 4 band EQ (
the Neve 1081 EQ plugin is one of my favorites for this) and sometimes compression and multibands - I boost and cut to try to make 1) the snare stand out more 2)the kick os emphasized 3) a hit hat or ride cymbal, fill, etc is emaphasized. Then you can pan each of these three tracks with the original drum track to give some dimension and then blend to suit. Use different Compression plugins or whatever on each track. And yeah it's munches CPU so I'll get balanced how I want in the mix and bounce some tracks to free up CPU. You can achieve a big drum or whatever doing many variations of the above. Pretty cool what cut and paste and right clicking can achieve.
There's my $0.02.