Does Valve interfere with Community Market prices?

i doubt it
sometimes the market servers may get overloaded and that's why some market transitions only show up later, for example during the last esl one katowice (free money /o/) i won a case and it took me almost half hour just to show up on market, and i also noticed that they all showed up at once

All they do is interfere with all the rules and restrictions they keep placing on/changing supposedly to safeguard us.

They don't need too, the Russian do it for them

Something like that? Probably money laundering. Not that I'd point the finger at any one nationality.

What you are describing happen when a user has an order that would fill their inventory, which is limited (in theory, not in practice) around 1000 items for CS:GO.

Valve is 'manipulating' the market but in other ways, they decide how much stuff goes into the market:
-The drop rate, and its schedule, and the amount of new 'Operations' and seasonal cases. Who would have guessed that Chroma 2 so quickly?
-In Dota 2, keys programmed extinction and The International Compendiums, but they mostly shut down its economy due to the game being f2p.
-I'm no expert in the TF2, but hats and buds were really a thing back then, and more recently, the introduction of Tickets.

Do you have any knowledge in markets/economics? All this make agents speculate through sell/buy walls and stocking stuff when cheap and selling slowly later on. Add to all these the kids that they don't know what they are doing and we have a mostly unpredictable market. It's really fun :)

In short, as stated by Varoufakis, the Steam market is a real economy, just without salaries or social benefits.

I would hope not, they are not some rinky-dink, fly-by-night company. They are a global entity and have many governments and other officials looking at how they maintain their service and conduct business. For them to interfere in their market and purposely fluctuate or conspire against their costumers, would prove to be the worst mistake they ever made.
Aside from Greenlight of course. And some Early Access. I joke, I kid... Not really.

I would assume the customers are the culprits of any interference in business as usual.

Those are most likely market bots