When we put negative mark at start, Autocomplete does not work.
For example;
if tes #=> test shows up.
if !te #=> no autocomplete
See below GIF:

Confirmed. This appears to be a simple bug in word detection. I should be able to fix it for the next release.
Fixed in the master branch.
Released in v0.32.0.
Most helpful comment
Fixed in the master branch.