Have you ever looked at it? If so, you'd realize everything you were worried about was nothing to worry about... as long as the company involved was *NOT* Microsoft.
Yet.. truncating this alleged-HTML-only (?) file, while producing a smaller file: does not produce -- when saved -- a file which can be loaded as a 'bookmark.html' file: to SeaMonkey et al. so far..
Of ocurse I may have missed something, like maybe first installing the small, default-bookmark file, then ... Importing, rather than just renaming above test files. (Not sure whether I tried enough permutations of that.)