Very sure. I started noticing the issue a couple of years ago (well before Musk's arrival) because I'd find myself thinking 'I haven't seen anything from ____ in a while, I should follow that person', only to discover that I was already following them and their tweets were just not showing up. New follows will generally pop up reliably, but if someone has fallen out of your regular feed you have to work to put them back into it.
Just now (as I am writing this comment) went to check on someone I saw an interview with the other day, and sure enough I am still following the person and they have been tweeting a few times a day, but I haven't been seeing any of it.
Other weird things are Twitter's habit of just preemptively muting people (I'll sometimes wonder why a person didn't reply and go back to reread a conversation, only to discover that they did reply; and conversely, people that I have muted or blocked showing up in my search results for a trending topic. Most of the people I manually mute are 'influencers' who use software, staff, or pure obsession to get in the first reply to politicians and the like, a behavior I find insufferably annoying even if I agree with their position.
I'm very interested in politics, but almost all my mutes/blocks are people of somewhat-similar political persuasion that Twitter assumes I would want to see, and insists on showing me despite my best efforts. I want to keep tabs on the arguments of people I strenuously disagree with, because I already know my own opinions and don't need validation. It's easier in some respects to maintain a second account with an uber-conservative persona and let the recommendation engine just feed it with more of the same.
That was the great thing with the 3rd party client, I could trust that all the people I followed I would get their actual tweets. Every single one of them. There was no also messing with it, no tweet "liked" by someone else, etc. Who I followed is what I saw, nothing less, nothing more.
Of course Elon banned those apps, so now I am on Mastodon where I see 100% of the content that I want. Bonus is that I can even follow many twitter users, through Mastodon bot mirrors. And of course, no ads.
It seems the only reason why people wouldn't show up then is that they got shadow banned or at least have some deboosting applied. So the algorithm thinks they are spam?
Just now (as I am writing this comment) went to check on someone I saw an interview with the other day, and sure enough I am still following the person and they have been tweeting a few times a day, but I haven't been seeing any of it.
Other weird things are Twitter's habit of just preemptively muting people (I'll sometimes wonder why a person didn't reply and go back to reread a conversation, only to discover that they did reply; and conversely, people that I have muted or blocked showing up in my search results for a trending topic. Most of the people I manually mute are 'influencers' who use software, staff, or pure obsession to get in the first reply to politicians and the like, a behavior I find insufferably annoying even if I agree with their position.
I'm very interested in politics, but almost all my mutes/blocks are people of somewhat-similar political persuasion that Twitter assumes I would want to see, and insists on showing me despite my best efforts. I want to keep tabs on the arguments of people I strenuously disagree with, because I already know my own opinions and don't need validation. It's easier in some respects to maintain a second account with an uber-conservative persona and let the recommendation engine just feed it with more of the same.