[Melian]

Can one display the international code of signals flags on a home flagpole to send a message to those that know their meaning? Is that bad form?

[LonePalm]

Yes you can. There are numerous places that sell appropriately sized flags for different sized masts.

That is not bad form unless you fly them from a single pole. Signal flags should be flown from the yardarm while the national ensign is flown from the peak. If the mast has a gaff attached and a club burgee is flown, the national ensign should be flown from the gaff and the burgee from the peak. See photo.

Numerous towns along the coast have a permanent display of the town's name in signal flags.

SpyNavy

Garde la Foi, mes amis! Nous nous sommes les sauveurs de la République! Maintenant et Toujours!
(Keep the Faith, my friends! We are the saviors of the Republic! Now and Forever!)
LonePalm, le Républicain du verre cassé (The Broken Glass Republican)

[OldWarBaby]

Signal flags? Not a problem. Fly “TRUMP” if you want. And if you really want to get into signals, stand out in the street waving semaphores. If your flag pole is big enough you could add a “MAGA.” And don’t forget you could also use the clothesline? Careful what you spell tho-—you might get an airplane landing in your yard?