According to the plugin author
You can edit the Spamwords field.
"investigate" is flagged because of *invest*
"pillar" is flagged because of *pill*
I believe the character * means 0 or more +, so any words with those characters will be flagged. I don't believe this is good practice. I'm not flaming the plugin, it seems like it can do quite a bit and has it's purpose.
If you want more control over spam words than what's built into WordPress, you should try the Better Moderation plugin.
I would use the Better Moderation plugin over this one for moderating words. It has better control over the words but also allows you to determine which if not all fields should be covered.
Depending on what you're actually trying to achieve, you might be better off just using the built in moderation tool and just input words that you would like moderated. There's a reason they built it into WordPress.
Here is a sample moderation list: