In his Deipnosophists Athenaeus pretty much talks about everything (e.g., the masturbation habits of the Achaeans during their nine years at Troy). Early on, he expands on good manners when coming to dinner at someone else’s expense (don’t go late) and the general creepiness of a man who dines alone (1.14.30-50):

“The comic poet Amphis says:

If someone comes late to a free diner,
Believe that he’d rush to leave the battle line too!

And Chrysippus adds:

Don’t make light of the free drinking party
A free drinking party shouldn’t be treated lightly, but pursued!

Antiphanes also says:

The life of the gods is this: whenever you can
Eat someone else’s food and think nothing of the bill.

And elsewhere:

This is the blessed life when I must always seek
Some new trick to find a nibble for my lips.

I came from home to this drinking parting bringing these lines, making sure as well that I arrived carrying my rent money too, since “we singers always sacrifice without smoke”.

The word monophagein [“to eat alone”]is used [negatively] among ancient writers. For instance, Antiphanes says: “You’re eating alone already and causing me harm!” Amphis, too, says, “To hell with you, you solitary diner, you thief!”

ἀσυμβόλου δείπνου γὰρ ὅστις ὑστερεῖ,
τοῦτον ταχέως νόμιζε κἂν τάξιν λιπεῖν,

῎Αμφις φησὶν ὁ κωμικός (II 248 K). Χρύσιππος δέ φησιν·

ἀσύμβολον κώθωνα μὴ παραλίμπανε.
κώθων δ’ οὐ παραλειπτὸς ἀσύμβολος, ἀλλὰ διωκτός.

᾿Αντιφάνης δέ φησι (II 117 K)·

βίος θεῶν γάρ ἐστιν, ὅταν ἔχῃς ποθὲν
τἀλλότρια δειπνεῖν, μὴ προσέχων λογίσμασι.

καὶ πάλιν·

μακάριος ὁ βίος, ᾧ δεῖ μ’ ἀεὶ καινὸν πόρον
εὑρίσκειν, ὡς μάσημα ταῖς γνάθοις ἔχω.

ταῦτα οἴκοθεν ἔχων εἰς τὸ συμπόσιον ἦλθον καὶ προμελετήσας, ἵνα κἀγὼ τὸ στεγανόμιον κομίζων παραγένωμαι.

ἄκαπνα γὰρ αἰὲν ἀοιδοὶ θύομεν.
ὅτι τὸ μονοφαγεῖν ἐστιν ἐν χρήσει τοῖς παλαιοῖς.

᾿Αντιφάνης (II 128 K)·
.. μονοφαγεῖς, ἤδη τι καὶ βλάπτεις ἐμέ.

᾿Αμειψίας (I 677 K)·
ἔρρ’ ἐς κόρακας, μονοφάγε καὶ τοιχωρύχε.