Twitter is known for experimenting with different features in its mobile apps and on its website. Its latest experiment — which treats favorites more like retweets on the main timeline — has some users seeing red.

A number of users are seeing tweets that users they follow favorite — or even popular tweets from accounts others follow — posted directly to their main Twitter timeline.

The Next Web reported on the new experiment, which has impacted users such as Re/Code's Peter Kafka, investor Hunter Walk and The Next Web's editor-in-chief Martin Bryant.

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

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

The experiments aren't dissimilar to some of the new notifications Twitter has pushed out, but because they take place on the main timeline — and because there appears to be no way to remove these new additions — affected users are responding with outrage and frustration.

After all, it's one thing to mess around with notifications; but the timeline is sacred.

From the screenshots that have appeared online thus far, these are some of the new additions that may appear in some users' timelines:

Tweets users they follow favorite (similar to the way retweets appear now)

Tweets from accounts a user they follow follows

The intentions for this experiment are probably to help increase engagement. One could even argue that for content Twitter deems to be "breaking news," putting important tweets from the accounts a person's Twitter friends follow into that person's main timeline could be valuable.

The problem, of course, is that this experiment is a big change to the way Twitter has always worked. Part of what makes Twitter great is that the timeline is relatively unobstructed. You see tweets from individuals you choose to follow and the tweets they choose to retweet. It's not like Facebook, where you also get information about every like, comment or recent game activity.

And it's not just prominent technology Twitter users that are getting the new timeline features. Celebrities are also being bombarded with these experimental tweets, too. And they aren't any happier about the situation.

.@joshgroban For real though.... cut it out twitter.— Anna Kendrick (@AnnaKendrick47) August 17, 2014

After spotting this tweet by singer Josh Groban — and the reply by actress Anna Kendrick — I favorited the tweet so that I could reference it in this post.

In a moment that was both ironic — and perfectly meta — that action was then shared with Bryant, who then shared the results with me.

Oh the the irony of Twitter showing me this @joshgroban tweet (cc @film_girl) pic.twitter.com/LeFcaVPk40— Martin Bryant (@MartinSFP) August 17, 2014

Perfect.

Retweets != favorites

To the best of my knowledge, I'm not seeing the new experiment on my account across any of my devices. I should note, however, that I almost exclusively use third-party Twitter clients — such as Twitterrific or Tweetbot — for viewing my timeline. For now, the experiments only appear to apply to official Twitter projects.

Still, based on what people I follow are sharing, I have a few concerns about the new way favorites are being displayed.

As The Next Web points out, favorites are distinctly different than retweets. A retweet is something a user intends to share with those who follow them. Favorites have an entirely separate social dynamic and their meaning is much more nuanced and personal to the user.

Some Twitter users utilize the favorite tool as a way of showing support or agreement with a position. Others might favorite a tweet they disagree with. I frequently favorite tweets I want to refer back to for inclusion in a story. And that's before we get into the various ways favorites can be used as a way to induce other actions, using services such as IFTTT or Pinboard. (For example, you can automate actions, such as saving links from favorited tweets to Pocket or Instapaper, or automatically bookmarking favorited links in Pinboard.)

Yes, the favorites made by a user are accessible from their profile page (assuming the profile is public), but the feature has always felt more private — or at least constrained to the user who favorites and the user whose tweet is favorited.

That said, entire social layers have been built-up around favorites, so the idea that Twitter could surface popular favorites to a user's followers isn't out of line.

As usual with these types of changes, the problem isn't so much the change itself, but the opaque nature in which it is rolled out. We reached out to Twitter for comment, but haven't heard back as of press time.

The company published a statement on its experiments last year, which provides a good overview for confused users. If we could make a suggestion, it would be for Twitter to notify users that are seeing an experiment for the first time what is going on — perhaps with a notification on the main timeline — along with a link to that blog post.