Reddit boss Steve Huffman has told BBC News he supported the aims of controversial sub-Reddit WallStreetBets.
A long-time fan of the group, he said he had been slow in spotting its effect on GameStop’s huge share-price spike in January.
“I was actually a little late to the party, because I didn’t realise that Reddit had leaked into the real world again”; he said.
GameStop’s share price ended up reaching nearly $500 (£350) before falling.
WallStreetBets had been hyping up the computer-game retailer’s shares.
The idea was if enough users bought GameStop shares, they could drive up the price; hurting hedge funds who had bet against the company.
Some claimed the group had collectively manipulated the market.
But Reddit decided to leave it up.
“We were… trying to keep WallStreetBets online,” Mr Huffman said.
When the media talks about the big social-media platforms – Facebook, Twitter, Instagram – Reddit is often ignored.
But as hedge funds learned during the GameStop share-price spike – ignore it at your peril.
Reddit likes to think of itself as different.
At its heart, it certainly feels more alternative.
Its system of upvoting content mean ideas either fly or die.
It’s not called the front page of the internet for nothing.
Mr Huffman has also had to deal with another big story this year – conspiracy theories peddled by Donald Trump about electoral fraud.
“What do you do when the president doesn’t live up to the ideals; like the principles of our country?” Mr Huffman said.
An influential sub-Reddit called TheDonald was instrumental in hyping up Mr Trump across the internet.
Reddit banned it last year.
Mr Huffman told BBC News it was the most difficult moderation decision he had had to make.
Huffman is one of handful of men in Silicon Valley – along with Twitter’s Jack Dorsey and Facebook’s Mark Zuckerberg; – that make huge decisions on what we can and can’t see on the internet.