But you should always use "i.e." because it's an abbreviation for two words. And I can't even think of a case that you wouldn't follow it with a comma (i.e., "i.e.,"), so that doesn't conflict with the ". " end-of-sentence pattern.
There are many style guides[0] that treat i.e., e.g. and the other Latin abbreviations specially in always punctuating them - it's rather rare to find someone talking about the former U.S.S.R., T.C.P. packets, or N.A.S.A.'s missions to the I.S.S. - to all intents & purposes, ie is the exception, not the rule. It's worth pointing out that i.e. is exceptionally difficult to type on a lot of mobile devices.
Comments
It's relatively common usage to omit the full stop when it doesn't signal a sentence end - ie like this. :)
But you should always use "i.e." because it's an abbreviation for two words. And I can't even think of a case that you wouldn't follow it with a comma (i.e., "i.e.,"), so that doesn't conflict with the ". " end-of-sentence pattern.
There are many style guides[0] that treat i.e., e.g. and the other Latin abbreviations specially in always punctuating them - it's rather rare to find someone talking about the former U.S.S.R., T.C.P. packets, or N.A.S.A.'s missions to the I.S.S. - to all intents & purposes, ie is the exception, not the rule. It's worth pointing out that i.e. is exceptionally difficult to type on a lot of mobile devices.
[0] http://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style#Abbre...