I think even underscore and backslash weren't necessary in computing, even though they were put to use once they were there. The @ was also really not necessary

I think even underscore and backslash weren't necessary in computing, even though they were put to use once they were there. The @ was also really not necessary. And a lot of those invisible characters weren't either. We should have had just one line break character, since the distinction between CR and LF makes no sense for computers, and certainly caused a lot of incompatibility. As you said, hindsight...