In many situations it's hard to tell the difference between lower-case L and the number one, or upper-case O and naught (the proximity of the latter pair on the keyboard makes this a particularly dangerous issue). But I don't eschew those characters; I choose fonts that make it easier to distinguish between them, and my text-editor's syntax highlighting will often (though not always) catch the difference. The tools can save you if you let them.

Similarly my text editor has an easy toggle (Ctrl+Shift+A) which can be done with one hand (almost with one finger on this laptop keyboard!) to show or hide whitespace characters (and Ctrl+Shift+D does line break characters) when I need to do a quick visual check.

But for the most part, when working on files that I've authored, I don't need to visually check because I know which characters will be tabs, and which will be spaces. In source code, the indents will all be tabs, and everywhere else will be spaces.

'There is not a "standard" for the number of spaces for a tab character.'

Indeed; that's kind of the point of them. You can set tab stops to whatever is most convenient for you. I like to use 3 column tab stops; other people might prefer 2, 4 or 8. If we all use a single tab character to indent source code, then we can all work on the same source code and see it with our preferred indentation.

"Or in a practical sense, the space saving makes no difference."

Indeed; if I were using tabs as a compression mechanism, I'd be an idiot. (Bzip2 works much better.) But that's not what I use them for; I use them because they make more sense in certain contexts (delimiting fields; indenting source code) than space characters. If there were a filesize penalty for using tabs, I'd continue to use them.

There is a disagreement of opinion here - not any disagreement on the facts of the situation.

Ok, there is more than one way to do it. I think fine.

I personally prefer fixed width font and no tabs within code. My normal program editor actually converts tabs to the appropriate number of spaces when I save the code to a file. I indent the code like I want. When I work in MS Visual Studio, it doesn't do that and I find it annoying - sometimes I want to take a MS .C file and use it on a Unix system and then we get into this "how many spaces does a tab mean?" thing. You see it as a plus. I see it as a hassle.

So I guess mileage varies. I have personally found the "|" (pipe character) to be a good field separator in many circumstances. When that doesn't work, then I go to full blown CSV with all the complications that involves. But there are some very good Perl modules that can parse this out albeit slower than simple split() or match global.