I don't think it is ever correct to omit a period (or full stop) at the end of a normal English sentence or indeed a paragraph.
But that is not to say that I don't see it "in the wild", and indeed, am guilty of omitting correct punctuation in a few cases where the sense is clear even without it.
I would omit a period at the end of a "sentence" that uses non-English words such as a fragment of code or a mathematical formula where any extraneous characters could lead to confusion or syntax problems. Example:
To fix the problem, use the switch /persistent:yes
Another example, in a presentation (ie projected on screen, PowerPoint, prezi, Keynote or whatever), I might use a series of bullet points without a closing period on any of them, not even the last. (I know! Heresy! Burn me as a witch!)
The next bullet usually makes the sense clear enough. The fragmented nature of the bullets often means they don't properly parse as a sentence anyway. In a formal text such as software documentation or training manual I would more usually ensure grammatical completeness.
To demonstrate as a meta-example, there are four reasons for this:
- it is just as comprehensible
- the next bullet arguably serves the same purpose as a separator
- I find it easier to be consistent in omitting them than including them
- everyone else seems to get away with it