A family of Microsoft word processing software products for creating web, email, and print documents.
I'm in tune with John on this...
When you Copy, it's the source program in combination with the OS that determines what variants are placed on the Clipboard [a service of the OS].
When you go to Paste, the program being used assesses what's being presented on the Clipboard & in which ways it can interpret that information.
The 'change' you're experiencing could be due to a difference in either or all of the 3 participants -- Source data format, Target program interpretation, OS Clipboard management.
As a wild guess, it also may be the file type of the document you're attempting to paste into. It appears that O2016 has taken another giant step forward in the effort to fully deprecate the old .doc file type. If you happen to be using it, see if you have a different experience when using a .docx file.