Playing a game I encountered two different shop keeps that say the same line. Only one says a line with a comma, the other says it without. I do know that commas can help in breaking up clauses in Japanese, but do commas have any impact on meaning in small sentences like these? Or does it more describe how it would be spoken?
また、来て下さいね。
また来て下さいね。
In general, using commas more than usual emphasizes a sentence (for example "Do, it, right, now."), and of course they affect how the sentence is read. But what is usual depends on the word. In this case, whether to put a comma after また is pretty arbitrary, and the difference between the two sentences is not really significant. Maybe the one with a comma would sound a little more emphatic or emotional, but I doubt the person who wrote this was thinking about the comma.
(A) また、来て下さいね。
(B) また来て下さいね。
Both (A) and (B) are used mainly in conversation having similar meanings, but as expected by the questioner, the nuances are slightly different between them.
Since (B) has no "読点｛とうてん｝ comma, it is pronounced continuously as a single phrase. This is a greeting that is normally used by the host side at the time of parting, both cases where the host really hopes the partner to come back to see the host again, and where it is told as mere formality.
(A) has a 読点｛とうてん｝, so a pause is placed after "また", then the following phrase is pronounced. In this case, there is a nuance that the host really hopes for the partner to come back to see the host again.
