Twitter is back in experimental mode, but its latest test is annoying people. A sizable number of users are seeing tweets favorited by others in their timeline, just like retweets. They are also getting notifications when others follow someone new.

This was first brought to my attention a couple of weeks ago, but Twitter appears to have widened the experiment to cover more users over the past few days. TNW’s own editor-in-chief Martin Bryant, Re/Code’s Peter Kafka and prominent US investor Hunter Walk are among those seeing these notifications.

Twitter filling my feed with stuff I didn’t ask for – stuff other people follow and fav. pic.twitter.com/IVOViGF1QW — Peter Kafka (@pkafka) August 17, 2014

Ooh now twitter inserting selected “[person you follow] faved” tweets into main timeline pic.twitter.com/zDhrNseNGs — Hunter Walk (@hunterwalk) August 16, 2014

Twitter’s recent experiments have been fairly innocuous — it removed Bing translations, hinted at commerce services, and began embedding tweets on the Web — but these new notifications are upsetting users because they are confusing and seemingly unnecessary.

Here’s a small selection of complaints I found. A Twitter search shows there are plenty to choose from, I could barely find anyone with anything positive to say:

Why does my twitter timeline randomly show me what people have favourited and who they follow? I don’t give a shit — rosie (@rosieminney) August 17, 2014

I DO NOT WANNA SEE WHAT PEOPLE FAVORITE ON MY TIMELINE THANKS TWITTER — beverly. (@breadverly) August 17, 2014

.@twitter so you’re showing what people favorite on my timeline now? Isn’t that what a RT is for? — Nathan William (@Treadzone) August 17, 2014

Retweeting is a core part of Twitter. People already know how to share items that they think will interest others. Favorites have emerged as something else altogether — a way to acknowledge receiving a message, say thanks, save a link for reading later (using services like IFTTT), and more. You can see a list of tweets a user has favorited from their profile, but favoriting is inherently a private action. That idea is turned on its head with this new experiment.

Beyond the effects of this update, Twitter’s continual tinkering of features that are core to its offering — remember when it tested replacing retweets themselves? — is worrying because it feels like those in charge don’t understand the basics of how the service is used. Rather than embracing new opportunities such as direct messages — which I wrote about last week — Twitter is changing its core features to make them worse.

There’s even been talk that Twitter might adopt a Facebook-like algorithm. That could mean content on your timeline is selected for you, and you don’t see every update from those you follow. That would be a radical move though, and it remains unclear if Twitter would actually make it.

Those currently seeing favorites in their timeline, and others concerned that the feature may roll out to them, can only hope Twitter sees sense and u-turns on this latest test.

Today is Sunday, but we reached out to Twitter to see if the company has any comment on its latest tinkering. The company often points media to this blog post, which explains that it experiments with new features on a regular basis.

Related: What I learned in my first year as a product designer

Headline image via Mary Turner / AFP / Getty Images

Read next: Exploring a new place? Moovit now provides trip information as you ride public transport.