Modify text appearance (put spaces after commas just for display)

[Alberto Luaces]

Hello, I have some inherited code where the style used was to squeeze
every single non-required white-space.  There are long lists of
comma-separated values with any spaces on them, rendering the code very
difficult to read.

I wanted to have something like glasses-mode, but unless I am mistaken,
it is not very configurable, so I cannot add new cases as commas
separated by spaces, which is mine.

Then I thought of overlays, but the manual says that if there are a big
number of substitutions, maybe it could be a better idea to use text
properties instead.

So, from the top of your head, what would be the less painful method to
change every comma to a comma+space, or at least change the color of the
commas to anything more distinguishable and attach it to the language
mode hook?

Thanks!

-- 
Alberto