"would have gathered" is a correct and usable part of a sentence in written English.
It is a past conditional verb phrase and is used to express an unrealized possibility or outcome in the past. It is often used in combination with "if" clauses. Example: If I had known about the party, I would have gathered my friends and attended.
One would have gathered basic information from all factory farms.
Students would have gathered round a patient to see this unusual phenomenon up close.
In the winter, shutters wouldn't have kept out the cold, and everyone would have gathered round the fire.
Normally, the group would have gathered first at Mr. Koch's Greenwich Village apartment for the requisite banter, capped by the obligatory argument over where to go for lunch.
Perhaps Webber, who scored 19 of his 26 points in the first 20 minutes, would have gathered some steam if he had been beside Williams.
Mitt Romney said that, if he had been president, he would have gathered information from "our C.I.A. bureau chief in Islamabad".
Maybe the mob wouldn't have gathered in the first place if they'd paid good money the night before to catch Jesus' show!? It's just not smart killing an investment you've made But no.
We would never have gathered friends and family to rejoice in a verdant state where we did not live.
"Listeners to the World At One on Friday would not have gathered that there is overwhelming scientific consensus that climate change is happening and that it is driven by greenhouse gas emissions and deforestation.
One pair of photographs shows Pozières on 17 June 1916, a village occupied by the Germans but still a place of old stone houses, barns, little fields, gardens, country lanes, and a small square where people would once have gathered under the trees.
Movement 7 finally picks up a line from the day's Gospel, verse 37, "how often would I have gathered thy children together, even as a hen gathereth her chickens under her wings".
