This is the sentence:
Before I could go far, though, something stopped me.
One thing was sure, though: he wasn't guilty.
Is it a matter of grammar or style? If so which version is more common?
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
Yes, you need the comma because "though" is parenthetical in this case. "though" has two meanings: (1) is synonymous with "although" and comes at the beginning of the sentence. (2) is used parenthetically to draw the listener's attention to an exception or "side note," if you will. In this usage, it can come in the middle (as in your sentence) or the end of a sentence - always set off by a comma.
Here is a helpful article on parenthetical phrases.