I am a prescriptivist and as such believe that there is a set way to format and punctuate these abbreviations (i.e., like this). I have noticed lately that the comma (and sometimes even the periods) seems to be left out pretty often. Is there a usage/style guide that now allows this, or are people getting lazy or “shorthanding” this on their own?
If it has become acceptable, I won’t like it, but at least I can stop yelling about not using something unless you can use it correctly.
If you are a prescriptivist, what do you mean by “optional”?
Interestingly it is not something that Word includes in their autocorrect. I was taught to avoid ‘eg’ and ‘ie’ wherever practicable and prefer to write out ‘for example’ or ‘as an example’ for instance.
According to WikiHow (hardly the final authority admittedly) "For American English usage, you should always put a comma right after both “i.e.” and “e.g.” as shown in the examples above. For British English usage, do not put a comma right after either “i.e.” or “e.g.”
I confess that this American wasn’t aware of the comma issue, i.e. I used the British convention.
Here’s a list of six style guides/authorities, and, basically, the US ones require or recommend the comma, and the UK one does not.
One not listed is Associated Press Style. I looked that one up and that style guide (which is usually leaner on punctuation than other styles) also requires commas after “i.e.” and “e.g.”
So, basically, it looks like Measure for Measure has the gist of it with being an American English vs British English issue. (I personally was also taught to generally avoid Latin abbreviations like that in preference to “for example” and “that is.” Chicago Manual of Style does not use i.e. and e.g. in running text, but does allow for it in parentheses and notes.)
I would wager that not only is it non-optional, it’s still required to be italicized.
I’m fast adapting to the notion that “Rules of Communication” are not even read by a majority of web-based “communicators.” That means you’re apt to encounter violations of all degrees online. Even newspapers and especially blogs are no more in line with what a good English teacher taught you than websites that espouse some new health remedy are with what health professionals propose.
If you can ignore the violations, do. It’s better for you mental health! 
I doubt that part. In fact, the Chicago Manual of Style says not to italicize it.
I am a descriptivist, but I agree with the op on this issue. While speaking out loud, we leave a pause after “that is” or “for example”, and I would like to put a comma here to signal this.
I don’t like the practice of italicising non-English words for the simple reason that I tend to assume that all English words were non-English (i.e., borrowed from other languages) at some point. I know this is not literally true, but this is true for a large fraction of the words.
Just curious, what do you mean by acceptable? I could argue that since you see it happening in text, it must, therefore be acceptable. If it weren’t, then it wouldn’t be showing up. But since you asked the question, I’m assuming you require a statement from a more august body than the discourse of speakers. So, what for you, would suffice to say, “This previously verboten phrasing or formatting is now ok”?
I understood the usage to be with periods, comma, space, text. That it what I stick to and consider correct and for me, correct = acceptable. I see a lot of things in text that are not correct, and therefore not acceptable, particularly for formal publications and documents at work. A typo is seen in text but that doesn’t make it acceptable. However, if there were some more official variant published by usage guides, rather than just folks not bothering to follow any correct usage, then it would be fine with me. I would use what I consider correct but I wouldn’t consider them to be wrong, because they are following an acknowledged variant format.
It is interesting to know there is an American/British difference on this one. Almost everyone I see not punctuating it the American way are Americans, but now I can nod thoughtfully at their choice to go British on that one.
I mean, as above, that maybe the rules have changed to allow them to (correctly) be omitted. I am a rule follower, but the rule has ot actually exist somewhere.
optional
You are referring to style, not grammar. Style has no rules. Period. Style guides are produced so that users can - should - be consistent in their usage in a world where rules do not exist. However, each style guide is different from every other style guide. (And many venues have their own series of exceptions to a standard guide.) That makes the concept that rules exist for style sheer nonsense. Nor can you possibly say that anyone is violating a style guide without having the same guide in front of you.
This is exactly why I hate prescriptivists so much. They talk about language, but they don’t know even the most basic underpinnings of the subject they proceed to accuse others of violating.
Wouldn’t it be more accurate to say that style has rules, but those rules are local (to a particular publication, institution, etc.) rather than global?
Why would you prefer such a needless feature? Nothing is lost by omitting the comma.
Oh, good; you can school me then. Is punctuation grammar or style?
I do the no periods thing, but I do add a comma. Seems to me there is no right or wrong here, unless you have someone supervising your writing style who insists that you do it a certain way (eg, if you write for a newspaper).
I prefer it because it’s right. If an American leaves out the comma, it tells me something about them (i.e., they trying to use a feature they don’t know how to use correctly).
There are American house style guides that proscribe against the comma in those abbreviations. (For example, The Journal of History of Philsophy, published by Johns Hopkins University Press, specifically says no italics and no comma after “i.e.” and “e.g.”)