It would be really overdoing things to include convolutions with more input functions in the sandbox article, but I plan a gallery-like page in the info still to be uploaded to gnu.org.
Development of the convolution theme includes other mathematical concepts. Far from being a "one-trick pony" you ought to know that the mathematics of the delta function, alone, lends itself to further visualization of subject matter routinely taught in dsp and related courses. Besides the ability to code, Development only needs imagination.
As the article indicates, I too made the mistake that Fortran was a dinosaur. Fortran is under active development, surpassing the performance of C in certain areas. I also code in C, Lisp, Scheme, and will be writing some code for C-Graph in Python - but modern Fortran remains a good choice for the core code.
There are websites that offer the demonstration of convolution, but none that encompass verification of the convolution theorem with ease, or that offer the range of features GNU C-Graph does. The download statistics verify C-Graph's growing popularity.
The meritless claim of "online promotion and documentation (marketing?)" has been recited elsewhere and is transparent in its intent.
Yes, you did miss the point. I won't comment on the other "significant" additional resources and external links listed in the articles on Convolution and Convolution Theorem, except that they hardly present "new science", which is not a requirement for a reference.
No, it's not possible to deflate my ego. I'm accustomed to these types of responses - and use them as building blocks.

Enough said. The reason more information on C-Graph is not already at GNU is because I find myself having to spend too much time dealing "blocks" in various forms. Wikipedians visiting this talk page have the text for the references should they choose to use them. Happy editing!

Avoiding more convoluted conversation.:) -