The documentation on Encodings in slick is pretty slim.
The Encoding page offers a little descriptive text for the Auto options, but very little on what exactly the others are (such as Text, vs Text sbcs/dbcs, or Binary vs BInary dbcs).
Also, seems a little out of date - since Slick seems to now support fixed-fonts in unicode. I'm not sure about the tab thing.
Unicode Limitations
The following is a list of Unicode limitations:
Proportional font tab character expansion is not yet supported. Since Unicode support requires the use of proportiona fonts, tab expansion is not fully supported.