See, eg, https://meta.wikimedia.beta.wmflabs.org/wiki/Special:SecurePoll/edit/17
Steps to reproduce:
Create a securepoll with:
poll type: Range voting (histogram range)
question: Question text
minimum score: -1
maximum score: 1
default score: 0
Use custom messages for column labels: enabled
custom messages: put anything for -1, 0, and 1
Save the poll, then go back and edit it
Expected result:
Existing custom messages for column labels are preloaded
Actual result:
Only the custom messages for -1 and 0 are loaded, the message for 1 is blank
I tried this again with -2, -1, 0, 1, and 2, and only 1 and 2 had there messages fail to preload. Perhaps its because they are positive?
The messages are still shown at the voting page though (https://meta.wikimedia.beta.wmflabs.org/wiki/Special:SecurePoll/vote/17)