Yet again, not sure how many people this applies to, but this question has not been answered anywhere on the internet, either in English- or Chinese-language websites.
As of the moment there is one tool I have found that will replicate, somewhat, the functions of 'Copy This' for Chinese. The app is called 语音输入 (as a new user I can't post links, but Googling "Windows Phone 語音輸入" [without quotes] is the surest way to find it). The app requires a launch before every use. To launch the app using voice and then dictate a note, the speech language must be set to Chinese (Mainland) (中文(中国)). Users must say 「开启」, followed by the name of the app, 「语音输入」. Users then need to press the microphone button at the bottom of the app and record their message, after which it will be copied to the clipboard. Windows Phone 8.1 apparently sees Simplified and Traditional Chinese as mutually exclusive, meaning that rendering 「语音输入」 as 「語音輸入」 results in an internet search rather than the launching of the app. Setting the speech language to Chinese (Taiwan) (中文(台灣)) or Cantonese (Hong Kong SAR) (廣東話(香港特別行政區)) is therefore not possible with this app, in spite of the fact that all three use Chinese characters.
If users do not care about opening the app using speech, the phone can be set to either Cantonese or Taiwanese Chinese. The app does a good job of recognizing both and will obediently copy the Traditional Chinese text to the clipboard. You are then free to paste the text into any app you wish.
However, a simple microphone on every keyboard would make life a lot easier. If users want to put English into Chinese messages (or vice-versa), they need to go to Settings -> Speech -> Speech Language, and change it every single time. Very, very annoying :eck: