Gee whiz, Erik, why not stop beating up on guys who simply want to do things differently than you would do them.
I do not care if someone does not do it it like I would (I have never stated MMIO is "bad" or even "not advisable" although I have abandoned it). What I argue against is things that STOP progress like the slovenness of the 8255. If the 8255 would run at "modern" I/O speeds i would be much more "gentle" in my arguments.

True, the 8255 isn't state-of-the-art, but there are LOTS of app-notes that do something some folks consider useful using an 8255.
In the uC business a decade is an eon, and using 20 year old appnotes, however recently they may have been reprinted, does not make sense.

there's no need to tell the guy he's a dummy, even if you do regard him as such.
I have not stated that anyone was/is a "dummy" making an unwise choice does not make you a "dummy", but not stating that the choice is unwise just to consider "feelings" more important than technical proficience does not progress make.

Again, what is useful about an experience "this can not run at todays clock speeds", but for the fact that some have to disregard the experiences of others and learn for themselves.

Erik