I don't agree with any part of that.

Before I go into any detail about why, note that to whatever extent your argument here justifies called CAD a ritual, it likewise justifies calling writing the word "duck" a ritual. The word is part of a larger system of symbolism and meaning, namely the whole English language. The letter "c" in the word is technically unnecessary in at least as strong a sense as that in which the DEL key in CAD is. It could have been omitted, or the "k" could have been, or the word could have been something like "ducq". Just as much arbitrariness.

And of course that all goes for pretty much any word at all.

A definition of "ritual" according to which everyone is performing a ritual every time they write any word is too broad. If everything is a ritual, then calling something a ritual tells you nothing interesting about it.

OK, so that's why I want your arguments to be wrong :-). Where are the actual disagreements? Well, on (b) I claim that that's not the sort of symbolism the paper is talking about.

"In rituals, the most ordinary of actions and gestures become transformed into symbolic expressions, their meaning reinforced each time they are performed". The symbolism of a ritual is supposed to have psychological or spiritual significance for the participant(s). The fact that CAD is one of a number of other keyboard shortcuts recognized by Windows is simply not an example of this.

The words I quoted a moment ago are followed by a few examples. Compare them with the alleged "symbolism and meaning" of CAD. "The repeated kneeling and bowing of religious prayer signals commitment to God and provides solace" (it signals an important fact about the person doing it, and it has a psychological effect on them); "a team's pregame ritual of putting equipment on from left-to-right (and not right-to-left) empowers athletes to perform at their best" (it has a psychological effect on them); "marriage rites during the wedding ceremony seal the bond between two people" (it constitutes a commitment they are making and it has a psychological effect on them). The so-called ritual of CAD has nothing in it that parallels any of this.

(If someone has a computer that frequently gets wedged, and has adopted a specific procedure where they first hold down CTRL and ALT, then say loudly and clearly "F### you, Microsoft", then hit DEL three times rhythmically, in order to express their hatred -- then that, for sure, is a ritual. It expresses something that matters to them and it has the psychological effect of helping them let off steam.)

So much for (b). What about (c)? Here's another quotation from the paper. "That is, rituals either lack overt instrumental purpose, or their constitutive actions themselves are not immediately causally linked to the stated goal of the ritual." Doing CAD has an overt instrumental purpose: it gets Windows into a particular state that you may find useful. Its constitutive actions -- holding down CTRL, holding down ALT, hitting DEL -- are immediately causally linked to the stated goal: if you do all those things, then Windows will (barring bugs, hardware failure, etc.) do what you are telling it to do; if you omit any of those things, it will not.

(In my example above of how someone could perform the CAD gesture in a manner that is ritualistic, note that I suggested that they hit DEL three times in rhythm. That's an unnecessary constitutive action. You only need to hit DEL once to get the effect; if you choose to do it multiple times, what happens doesn't depend on whether you do it rhythmically.)