i.e. and e.g.
A quick observation this morning as I was brushing up on a couple of grammatical things over at Grammar Girl while finishing a book chapter: Concerning the abbreviations i.e. (that is) and e.g. (for example), most American English dictionaries seem to suggest that they should be followed by a comma, while in British English it is fine to leave the commas out. That said, abbreviations generally makes a text less approachable, so you might want to spell out the words in plain text....