I don't know how outdated it is though.
Should there be a comma before though, as in the following?
I don't know how outdated it is, though.
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Though is used as an adverb in this case, applied to the verb is, therefore no comma is strictly necessary.
Saying this, I can easily imagine a brief pauses between is and though when speaking the sentence, hence a vocative comma is acceptable.
In other words, take your pick. If I can avoid a comma (as in this case), I usually will. It's not wrong either way though.
I'd use the comma, but modern style would probably omit it. There is a general tendency towards less punctuation. Look at Victorian novels, and then compare with modern prose - there is much less punctuation now. Or look at the King James Bible; that is rife with colons and semi-colons that would not appear nowadays, often not even 'demoted' to commas. Punctuation style has changed over time.