It's a good exercise to try to spot when you're accidentally spreading disinformation. We'd all be better off if we took a second before posting something we think we know, to ask: wait, is this a real thing or is this bullshit?
Here we have the idea that you can do the secret handshake incorrectly and thereby invalidate what most countries view as an automatic right (copyright usually doesn't even require any notice) and that adjudicating judges would shrug and say "Sorry, you used parentheses: my hands are tied. They're free to copy you", based on some random book from the 90s that was likely also full of bullshit. Does that sound right to you?
It's a good exercise to try to spot when you're accidentally spreading disinformation.
You might want to ask yourself that very question.
based on some random book from the 90s that was likely also full of bullshit
Nah, it was an excellent book that I pored over.
I don't understand why you guys are so confident with zero basis for your position other than "I'm so used to seeing it that I assume it's legally valid".
As I explained already, "(c)" is gibberish. Go ask a lawyer if you should put meaningless gibberish in the middle of legal disclaimers.
Fun fact[1], © gives some additional protection worldwide, but in the US simply writing "Copyright 2021" gives you full protection. Meanwhile, "(c)" doesn't actually mean anything, doesn't gain you any worldwide protection like © does, and arguably invalidates the rest of "Copyright (c) 2021".
[1] that might not even be a fact anymore, as I learned it from an excellent book on copyright in the early 90s, when DOS made "(c)" ubiquitous.