If you are going to edit the file anyway, as this hint has you do, why don't you just change the extension to .txt?

For the most part, text files that I make already have this, so this is mostly for things that are from something else, when I usually don't want to edit the file, extension or creator code. In that case, I use the script that I posted below.

I run a lot of numerical simulations. It is quite useful to give the files these simulations output meaningful extensions, eg, .log, .dat, .param or something even more specific. It is simply my way of already sorting these files into categories. I also use partly code written by others which had their own conventions.
Most of simulations are run on Linux workstations, with files created by Fortran, C++ or Perl. I essentially was just curious what possibilities there to make them quicklookable.