multi column sorting does not work

I have seen a JIRA 2.6.1 installation which allows sorting by several columns. The header block in the "Printable" browser display displays:

"Sort by: Status ascending, then by Updated ascending, then by (third column)".

Whenever one clicks on a column head, the sort is performed by this column first, then by the column selected before etc.

However I am unable to reproduce this on other JIRA 2.6.1 Enterprise sites. When clicking on the column header in the "Printable" view the table is redisplayed sorted by the new column, but it is not sorted by the previous column. Also the header block displays "Sort by: (column)" only, without the "then by: (second column)" part.

The user owning the JIRA site with the multi column sorting capability also reports that this feature does not always work.

So the two questions are:

1. how do I enable multi column sorting on my JIRA 2.6.1 site?
2. how do I make this working reliably?