Anyone can self-host the software on their own server. Users can join an instance they like.
You can view and comment on other servers (instances) as long as the instance you are on hasn't blocked the other instance.
Frizbee is built around anonymity. The site automatically creates an identity for each visitor and the visitor can create multiple other identities freely. The site even offers an easy way to manage identities. These identities can be temporary or saved with a passphrase for later use.
Cyberbullies are warned and removed from the forum the moment they display patterns of harassment or vicious behavior. It's not about the topics or opinions, it's about communicating like an intelligent person rather than a troll.
While Slicer is a passion project for the site's only developer and there are no real issues currently, the rate at which the site improves and how it is handled is solely in the hands of one man. One point of failure may be an issue for some.
Stacksity automatically embeds images and videos in the feed instead of requiring to navigate to a different site or having to manually click to show each separate item. It allows getting through a lot of images and videos quickly.
Darto has a significant amount of features that reddit doesn't have, specifically made to improve the experience over reddit - a different approach to moderation, a larger importance on relationships, unique community customization global tags, other reactions, etc. Definitely worth checking out if you are interested in an alternative.
Reddit users won't be instantly familiar with the newer features that this platform has, and it takes a fair amount of time to get comfortable adjusting to it.
Voat is essentially a Reddit clone. It uses Reddit's layout and basic functionality with only minor tweaks and as such will be instantly understandable to anyone who is familiar with reddit.
Voat can't yet handle large groups of people visiting the site all at the same time. This results in the site often being down. Many argue that the main issue is choice of underlying architecture (ASP.NET + MSSQL) that is difficult to scale.
If you're looking to get famous for your writing, this might not be the best place. It's a small community. It looks to be growing so maybe you could make a name for yourself there if it blows up.