lesspipe.sh has some special matches to handle compressed man pages, and
checks after decompression that these are man pages. It doesn't have
backups incase it was just a normal file with a name which matched (eg less
patch-2.4.1.bz2 just displays the compressed input)

To fix, change the first two cases to be:

  *.1.gz|*.2.gz|*.3.gz|*.4.gz|*.5.gz|*.7.gz|*.8.gz|*.9.gz|*.n.gz|*.man.gz)
    if gunzip -c "$1" |file - |grep troff &>/dev/null; then
      gunzip -c "$1" |groff -s -p -t -e -Tlatin1 -mandoc - ;
    else
      gzip -dc "$1"  2>/dev/null ;
    fi ;;
 
*.1.bz2|*.2.bz2|*.3.bz2|*.4.bz2|*.5.bz2|*.7.bz2|*.8.bz2|*.9.bz2|*.n.bz2|*.man.bz2
    if bunzip2 -c "$1" |file - |grep troff &>/dev/null; then
      bunzip2 -c "$1" |groff -s -p -t -e -Tlatin1 -mandoc -
    else
      bzip2 -dc "$1"  2>/dev/null ;
    fi ;;