I was wondering if your bot also looked for the user ID as well as the username. (I check the OP, it is seams that it is not yet the case).
Like if someone writes guigui371 I get notified but If someone writes my profile link, I don't.
https://bitcointalksearch.org/user/guigui371-207818 or even if someone is referring to me as just my ID : 207818
For my personal use, I would say that this is not something that matters to me.
But it could be useful for other members that may et referred to by their profile link or user ID.
I guess this matter will be solved once you set up the "keywords"