increasing number of Recent Comments in sidebar

I’m not familiar with that theme , but a great and configureable plugin is Get Recent Comments:
https://blog.jodies.de/archiv/2004/11/13/recent-comments/

Edit** Sorry missed the fact you’re on wordpress.com – wrong forums.

A wordpress.com account does not let you edit your theme templates.

michaelscomments.wordpress.com
The right forum for your question is here:
https://wordpress.com/forums/

moshu, sorry.
IanD, thanks for the reply. That particular template lets us use our own image for the header, so I thought there might be another tweak I couldn’t find.