Precedes the reason/cause B for the (strong) feelings/emotions A
The term that precedes こと に is either an emotion, feeling (such as 悲しい, or 面白い), or a resultant state (such as 困る).

驚いたことに、髪が生えた。
How surprising - I grew some hair!
15
うれしいことに彼女は試験に合格した。
To her delight, she passed the exam.
6
その事件以来、面白いことに、犬猿の仲だった二人はすっかり仲良くなってしまった。
Interestingly, since that incident, those two (who had been at each others' throats) have become quite good friends.
9
もったいないことに、彼はサッカーを辞めて就職するそうだ。
Such a waste: I heard that he quit playing soccer and is searching for a job.
Getting the sentences
Construction
(Elements in parentheses are optional.)
Where this grammar is found
Grammar usage notes
More common in written language, but not exclusively.
Questions/Discussion
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