In your originating major mode, if you can use (forward-comment 1)
then the semantic will also be able to ignore your comments.
This doesn't appear to be the case necessarily, in since the file
consisting of one comment
/* ignore */
withmy simple-mode.el as in the mail I just sent,
M-: (forward-comment 1) works, but M-x bovinate produces only
simple-lexer: Unmatched Text during Lexical Analysis
If you do not have, or wish to have a major mode, then you can
instead set the variable comment-start-skip and tweak the
semantic-lex-syntax-modifications according to major mode rules.
After this, you must make sure that `semantic-lex-init' is run.
If you do those changes in your setup function then the rest of
the harness will find them and use them.
I'm surprised by the above result, and I do have a major mode, but
I can try working along these lines too... though any feedback
on why the other route isn't working would be helpful.