The example below is taken from the wiki article "Titles 
<http://wiki.contextgarden.net/Titles>," with pdf bookmark apparatus 
prepended and a second chapter added to the bodymatter.

In the log, this produces the lines:

    backend         > bookmarks > confusing level change at level 3
    around '1 body'
    backend         > bookmarks > confusing level change at level 3
    around 'A appendix'
    backend         > bookmarks > confusing level change at level 3
    around 'back'

That is, one message for each *matter change.

What is the meaning of the message, and how can it be removed (short of 
disabling pdf bookmarks)?

    \setupinteraction[state=start]
    \placebookmarks[chapter, section, subsection, subsubsection]
                    [chapter,section]
    \setupsectionblock[frontpart][page=]
    \setupsectionblock[bodypart] [page=]
    \setupsectionblock[backpart] [page=]
    \setupsectionblock[appendix] [page=]
    \definepagebreak[firstpagebreak][yes,header,footer,right]
    \setuphead[chapter][page=firstpagebreak]
    \setuppagenumbering[alternative=doublesided]
    \starttext
    \startfrontmatter
    \chapter{front}
    \stopfrontmatter
    \startbodymatter
    \chapter{body}
    \chapter{body}
    \stopbodymatter
    \startappendices
    \chapter{appendix}
    \stopappendices
    \startbackmatter
    \chapter{back}
    \stopbackmatter
    \stoptext

-- 
Rik