I have a feeling that there is a lot of professional manipulation being done on Reddit.
Practically all posts that encourage people to do something about their digital freedom and privacy, the post gets downvoted and comments contain all sorts of pro-corporate statements.
Even in case of posts that are just links to news or videos, without any additional opinions by OP.
Is there any research about this phenomenon?

You asked a question, let’s see if we can all work on an answer.
I don’t even know what journals would publish such research. Starting with Google Scholar to get an idea of where to look for more information.
Just looking for reddit:
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C24&q=reddit
Adding some search words:
https://scholar.google.com/scholar?hl=en&as_sdt=0%2C24&as_ylo=2025&q=reddit+manipulation
The top, for me, result is: “Debunking a politically motivated rumor on Reddit: the context of the 2024 U.S. Republican presidential campaign” from “Journal of Documentation”, which sounds fake (not my field).
https://www.emerald.com/insight/content/doi/10.1108/jd-02-2025-0052/full/html
Clearly, one should not restrict themselves to the first journal that seems to touch on the subject. Please attempt both a depth and a breadth search, switching as personal energy and interest levels shift.
Searching the Journal of Documentation for reddit:
https://www.emerald.com/jd/search-results?page=1&q=reddit&fl_SiteID=1000445
And now one can engage in weeks of reading and reviewing papers.
It is my hope that others already have the knowledge to shorten this search.
Edit: “Understanding Reddit” by Elliot T. Panek looks interesting, but is a whole book.
https://www.taylorfrancis.com/books/mono/10.4324/9781003150800/understanding-reddit-elliot-panek