First, I thank my God through Jesus Christ for you all, that your faith is spoken of (rather, proclaimed) in the whole world. We observe here, as in other Epistles, St. Paul's way of beginning with complimentary language, and expression of thankfulness for the good he knew of in his readers.
He thus intimates at the outset his own good feeling towards them, and predisposes them to take in good part any animadversions that may follow. "The whole world" is not, of course, to be taken literally, but as a phrase denoting general notoriety.
Similarly in 1 Thessalonians 1:8, ἐν παντὶ τόπῳ. Any considerable number of converts in so important a place as Rome would be likely to become notorious in all Christian circles, and even outside them might have already begun to attract attention.