The other day, failing to notice that the blog on which I'd left a comment (and now can't even find) about "alt-", is puzzling: unless it means nearly the same as "neo-" did several years ago in political discussions, it would be a truncated form, as "lumis-" and "paci-" frequently are and as such easily confused with the German "alt-", meaning old, and too similar to Latin "altus", referring to height but doubly unclear when truncated.
The author of the now-defunct blog post explained with several current, published examples that it means alternate or alternative. My comment suggested that between German and Latin look-alikes, familiar to older readers, this confusing one should be abandoned.
Then, one of those dawnings that happen when one is about to fall asleep: it's not "alt-" but ALT on the PC keyboard. And as such it may be useful, to rid us of those strings of asterisks or hyphens ; it would be unambiguous when undergraduates or political candidates or comedians used words that networks bleep and the print media replace with those century-old asterisks, thus: ALT+F, et al.