I want to insert TAB characters inside a TEXTAREA, like this:
I can
Unfortunately, manipulating the text inside textarea elements is not as simple as one might hope. The reason that Tabby is larger than those simple snippets is that it works better. It has better cross-browser compatibility and handles things like tabbing selections.
When minified, it's only about 5k. I'd suggest using it. You'll either have to discover and troubleshoot those same edge cases yourself anyway, or might not even know about them if users don't report them.