It should break before the text コミュニ because of the zero-width breaking space before it, and the zero-width non-breaking spaces between the characters. The second example shows what happens with breaking/non-breaking spaces, which work properly in firefox. The spans are added purely to show what's going on -- the bug occurs without them.

サポート、イベント、​コミュニケーション。

サポート、イベント、 コ ミ ュ ニケーション。