So I didn't even know avatars were a thing on Reddit because I've used sync for so long. After migrating to Lemmy this is a thing I noticed they have and I actually added one. Will S4L include these? It's not a huge deal I'm buying it anyways, just curious if it will be added to it.
Lemmy doesn't have "their own app" nor does it have "its own site". It's all open source. There is no one company behind it. The one issue that might arise is that the open source project is being led by a bunch of developers who could in theory go rogue, but people would just create a fork (kinda like a copy) of the source code and create their own lemmy instances. On top of that, Lemmy instance admins would likely not install the updates from the main developers.
"here" is subjective on federated platforms. If the people running kbin.social or lemmy.world go full Spez/Musk and start doing restrictions and ads, there's nothing to do but leave. It's just easier to leave when a fair amount of the communities you're in aren't hosted on your home instance.
If there are missing features from the Lemmy API, that can be requested or even someone can implement them themselves. Pending approval from the project maintainers, they'll be made a part of the main branch of Lemmy and thus all updated Lemmy instances will have access to these new API features.