Also since it looks like it's a problem with Modo's N-gon triangulation mechanism, you should probably be able to repeat the problem if you manually created an N-gon with that same vertex structure.

Triangulation of N-gons is a fairly tricky business and there are certain kinds of shapes that tend to be more difficult to process and are more prone to making messy output, and one of those is areas where there are several nearly but not quite exactly colinear points in a row.

- Michael