I believe Netscape 7.1 is the minimum version supported. Prior versions were based on the Mozilla 1.0 code branch (as evident in the "rv:1.0.2" section of the version you pasted), while 7.1 is based on the Mozilla 1.4 code branch (It shows rv:1.4 on my copy). The necessary support for the advanced editor was added to the Mozilla engine ("Gecko") around 1.3.
Jason Rhinelander
Gossamer Threads
jason@gossamer-threads.com
Jason Rhinelander
Gossamer Threads
jason@gossamer-threads.com