I'm designing one specific medical application and got stucked with autosuggestions.
The idea is to write a post and include medical terms in it and do it without tag system. Should work like this: While typing device recognizes the terms and convert them into hyperlinks with explanations.
The main problem is to have an easier input for these terms and use autosuggestions. Terms are so specific that usual keyboard suggestions can't help with it. Maybe in the future we will work on AI, but now it's out of scope. Another problem is cases and plural forms.
One of the solutions could be to use so-called Tap-Ahead interface, I added wireframes for that.
Another solution is to have a kind of switcher to the term-writing mode. But it's the same as to have a tag system and requires an additional tap. Also wireframes.