They're always edible, but when they flower the 'bulb' is small and hollow. The bulb and the stalk especially tend to be tough compared to normal onions, so you should dice it up smaller than you otherwise would and that won't be a problem. I think they're a little less pungent too. I used one for tacos the other day in a pinch...

Let it go to seed and collect your own seed for next year. You could even try breeding them for certain traits or cross different varieties to get interesting hybrids. Growing your own unique creations will be incredibly rewarding.

If the flower buds are still very young and small, snip them off.
This way you may get a regular onion. Or, as suggersted, let them flower and collect your own seeds later.
I plant my dehydrated, sprouted onions very early spring just to flower and make seeds.They have pretty flowers that last for weeks.

Why do you dehydrate sprouted onions? How do you dehydrate sprouted onions?

another newbie :-)