The comma is omitted when such an apposition is used as a single phrase or a compound name.
The poet Longfellow was born in Portland.
The word patriotic is now in extensive use.
13. After phrases and clauses which are placed at the beginning of a sentence by inversion.
Worn out by hard wear, the type at last became unfit for use.
Ever since, he has been fond of celery.
The comma is omitted if the phrase thus used is very short.
Of success there could be no doubt.
14. Introductory phrases beginning with if, when, wherever, whenever, and the like should generally be separated from the rest of the sentence by a comma, even when the statement may appear to be direct.
When a plain query has not been answered, it is best to follow copy.