in iOS 9, you could select text, then tap on the selected text, and see a number of options (formatting, share..., and others).
Now in ios10, you only see the "Share..." choice if you have selected just one word. If you select more than one word, then you see only Copy, Sect All, or Look Up.
This happens only in mail, not safari.
THe the reason this matters for me is that I used to use share send text to my reminder app, "Things"
i think this is a bug.