Thus saying, I've done some IndentHL syntax updates. It now has a couple new features (and settings!):
- Error highlighting: if you have a line indented with a combination of tabs and spaces then this will highlight it as an error.
- 'follow the expandtab' setting: If you turn off the expandtab setting then the syntax plugin will highlight anything that isn't TAB'd out as error prone. If you specify et then the syntax plugin will do its same 'indent level highlighting' it did before for spaces (using your shiftwidth setting), and it'll highlight in red anything thats tabbed.
- A setting to turn off error highlighting: maybe you don't care about consistency. Well, you can turn it off.
- I originally designed three different highlight modes (see my original post). You can now pick which one you want (as a setting).