My terminal emulator is configured for Unicode character encoding and my .vimrc contains the line
set encoding=utf-8
but when I try pasting
Instead of copying the character from the clipboard and pasting it into the text editor, you can add it to the file using vim's digraph feature.
So, with default settings, using your example, you could enter insert mode, then hit Control-k, and type e'. The result will be é.
You can see the list of defined digraphs by running
:digraphs
and general help by running
:help digraph
which also explains how to customize your mappings.
If you are truly set on pasting the characters in, Shift-Insert has always worked for me.