Tangentially, http://www.shellcheck.net/ is an awesome static linter for shell code. Available online, as a command-line tool, but most importantly as a plugin for your favorite $EDITOR.
Whenever I attempt to learn a new language I find that static analysis tools and linters, if available, help me get over any initial confusion about what constitutes good idiomatic code. Guides like OP help too, but nothing beats a good linter. The thing is though, I've been writing Bash shell scripts for going on 15 years now, and I still overlook little details [0] all the time.
I've been mulling in the back of my head for a while a theory about the need for style guides and linters: if a language makes them a near necessity for reasons other than aesthetics then the language is probably best avoided. I'm not sure if agree totally with that. However, I think the most frustrating experiences I've had while programming are the result of languages which allow for multiple ways, in terms of syntax, of doing the same thing which behave the same most of the time.
When writing bash, there are so many hoops to jump through (e.g. syntactic traps, bashisms to avoid) that people who like me who use these languages only occasionally will shoot their foot repeatedly.
For this population (and I think it's big, given the glue nature of *sh), a guide won't help much because occasional practice won't give them any time to sink in; interactive linters are a godsend.