One of my pet peeves is the use of tab characters for alignment. Sure, this might have been acceptable in the early days of computing. But it’s really not a good idea any more.
Tabs display differently depending on the settings, since they do not come built-in with an alignment configuration.
Rather, tabs should be used for delimitation. For instance, separating the values in a table with tabs is often superior to doing so with commas.
Tabs should not be used for indentation. This is true of both code and word processor documents. Spaces are much more portable and flexible. The TAB key, on the other hand, is a perfectly reasonable shortcut for an editor to automatically indent code with spaces, or for a word processor to apply the appropriate indented paragraph style.
Multiple tabs should not be used to make tables look “nicer”. It’s the responsibility of the editor to display TSV files in a sane format; using multiple tabs is simply not portable and semantically wrong.
I realize this is a somewhat contentious topic—some people to this day still prefer tabs to spaces for indenting code, for example. My personal view is that indenting code with tabs is utterly ridiculous. I don’t personally see why this is even a debate.