The optimum solution for me would be one where I can use my own insert handler without the IDE inserting anything on completion.
One of the reasons for this is that Markdown completions make the most sense when not case sensitive, but the IDE tries to match case of inserted text to what is already there and it completely messes up the suggestions which are already case adjusted.
Right now I resort to replacing the IDE inserted text if the lookup item is not case sensitive.
I also want to leave auto-pop up suggestions on in plain text completions in my plugin but for touch typing and no syntax for guidance almost every word will match some suggestion, making touch typing impossible with on space completions. However, having the suggestions pop up is helpful and hitting tab or enter if desired.
If I could completely take over the insertion of text then I can kill two birds with one stone: prevent space char completions and insert exactly what is intended without having to remove the IDE inserted text first.