Two good Dutch expressions like this are "erg goed" (awfully good) and "zeer goed" (sorely good, which means 'really quite excellent'). As to what I think of the phenomenon, I think it might have begun as a device to ward off the jinx involved in calling something really good. Tell any novelist that their book is really really good, perfect, and they will rapidly or even nervously tell you that it was really all hard slogging and research and yes, they had hoped to get it right to some extent and were glad you felt that the work had been worth reading.
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