We didn’t skip 4.1.5. It just lasted a very short time so I didn’t have the time to write an announcement. So I’ll just collapse changes from both versions here for simplicity.
Performance improvements
We’ve made some performance improvements especially in the local message database part. There is still room for improvement; for now we fixed a long-standing performance issue caused by first opening a large conversation after receiving a few new messages. More performance fixes will be on the way to make Kontalk the fastest app alive (pun intended).
Attach button moved to the composer bar
The attach button was moved from the toolbar to the composer bar (at the bottom). For now, the same panel will appear as before.
Archived chats
Version 4.1.5 introduced the concept of archived chats. You can archive them by long-pressing on one and choose the Archive menu item. There isn’t an archived chats screen yet, but we’re working on it.
An archived chat is restored by starting a new chat through the new chat button in the main screen or when receiving a message from the contact.
Special background filter for unencrypted chats
If you disable encryption in chat, Kontalk will now remind you by adding a red filter to the chat background.
Number of online people in a group
Kontalk will now show a count of online users in a group in the toolbar. Note that the count includes yourself. Though this might seem weird, first, you’re actually online and in the group, second, we plan to introduce observer membership in a group - and that would not show yourself in the online count since you’re not participating in the group, but just observing.
New emoji version (or not)
For some of you having 4.1.5 working nicely, you may have noticed new emojis. 
This is the main reason for 4.1.6 coming out right after 4.1.5. Some devices - especially low-end ones - were reporting out of memory crashes. This is due to a new approach used by the emoji library. The idea is great because it gains in speed, but consumes more memory. Hence the crashes. Until I find a solution (I’m doing some tests and I hope I can contribute a fix to the library myself), I decided to revert to the old version.
Road to Kontalk 5.0
As per our guideline roadmap, I’ve been working on making modifications toward Kontalk 5.0 and the introduction of OMEMO. It’s still a long way to that, but I’m confident we can reach it.
Bug fixing
A lot of those. Seriously.