A Victor Mair post at the Log discusses the issue of Chinese borrowings from Japanese (with links to earlier posts on the topic), focusing on a striking recent example:
The word “desu です” is a copula that occurs at the end of a statement sentence in Japanese. In Mandarin there was originally no such sentence final copula. However, in contemporary internet language usage, it is fashionable among Chinese young people to add deshuō 的说 (lit., “X’s saying”) to the end of sentences. Though many of them may not know the origin of the expression deshuō 的说, despite their being fond of using it, it is most likely a usage borrowed from Japanese.
Here is an example showing the phenomenon:
English: It is very cold today.
Japanese: Kyō wa totemo samui desu 今日はとても寒いです。
Standard Mandarin: Jīntiān hěn lěng 今天很冷。
Sino-Japanese (Mandarin with Japanese characteristics!): Jīntiān hěn lěng deshuō 今天很冷的说。
This is a phenomenon I noticed back around 2008 […], but I am only prompted to write about it now because in recent years so many of my students from Sinophone countries have developed such an enthusiasm for learning Japanese. […]
Bilingual (Mandarin and English) Chinese colleagues have explained this usage of deshuō 的说 as being roughly equivalent to “it seems that; it is said that”. Monolingual Chinese have told me that they think of deshuō 的说 as meaning roughly jùshuō 据说 (“reportedly; it is said that”).
A trilingual (Japanese, Mandarin, and English) Japanese colleague suggested to me that deshuō 的说, rather than deriving from desu です, may have come from deshō でしょう (“it seems that; I suppose; perhaps; would”), the volitional form of desu です.
So far as I can tell, sentence final deshuō 的说 is used primarily by teenagers and young people in their twenties.
There is, as usual, good discussion in the comments.