I cannot reproduce this, I added a test case that shows that it works. The plugin is downcasting the nick name before saving it and when checking it against remembered notes.
I can't reproduce it anymore too:
[12:37pm] Ant> @note ant test
12:37PM Flexo> done, Ant
[12:37pm] Ant> t
12:37PM Flexo> Ant, you have notes! [Apr- 7 12:37] test