Minor issue and maybe no easy fix.. I'm just reporting this... don't need any quick fix.

In the activity stream if you post an email address in brackets.. such as "Contact Sarah (sarah@example.com)" then the system is clever enough to know it is an email address and creates a mailto link but it includes the brackets in it.. so it creates mailto : (sarah@example.com) which of course will fail.

I know it's probably not a good idea to post email addresses like this anyway, but my users do from time to time.. and just reporting this issue that I've seen.