I found a small bug in Blog.BlogCode. A wrong query string for the
 paginated view of blogs is created.
 I found it in version 3.5.1, but it is also in version 4.1-20120711
 (current 
myxwiki.org).
 At line 751
 751:             #set($queryString = "${queryString}&${p}=${v}")
 Correct is
 751:             #set($queryString = "${queryString}&${p}=${v}")
 Should I submit an issue in jira? If yes, what project, Issue type and
 should it have.
 
Indeed, that was a bug. I took the liberty of committing your proposed
fix already: