Summary

These problems are similar with HCPUB-19. But different at its behaviour.
There are 2 problems found when input double-byte characters and convert it by calause in HipChat message.

1. Input text string in message field disappears when user converts it to a conversion candidate and moves target clause by pressing a left arrow key.

How to reproduce
1-1) Open HipChat client and try to input message (both room and private are possible)
1-2) Type double-bytes characters like 'にわとりがいる' in Japanese　
1-3) Press space key to convert to first candidate (the srring devided into clauses like this |にわ|とりがいる|)
1-4) Press "shift key" + "left arrow key" to change a clause division (try to change clauses like this |にわとり|がいる|)
1-5) inputed string disappears

2. Input text characters are not deleted as expected when user press backspace key.

How to reproduce
2-1) Open HipChat client and try to input message (both room and private are possible)
2-2) Type double-bytes characters like 'あいうえお' (5 chars) in Japanese.　
2-3) Before convert the string by pressing return key, press 'backspace key' 5 times to delete a input character.
2-4) The last character cannot be deleted at 5th backspace key (but can be deleted at 6th backspace key).

HipChat client
Version 4.0.1637

Platform
Windows 10 (x64 TH2/Pro Insider Preview)
Windows 8.1