The Multi Issue Key Searcher field currently requires commas between issues to work properly. The best solution is to be more flexible (specifically, allow simple whitespace). However, documenting this requirement in the description below this field would at least mitigate the problem.

The existing descriptive text reads:
"Multi Issue Key Searcher - allows you to enter multiple issues for searching."

You should modify this to say:
"Multi Issue Key Searcher - allows you to enter multiple issues for searching. Separate issue keys with commas. "