A search for how to change the header image led me here — thanks so much for putting this child theme together!
I’m having the same problem, and I’m running PHP 5.4.14 on amycavender.org.
The plugin appears to install correctly, but when I try to network activate, I get the following: Parse error: syntax error, unexpected T_STRING in /home/cavender/public_html/wp-content/plugins/Twitter-Mentions-as-Comments-master/twitter-mentions-as-comments.php on line 110
Any suggestions?