How do I style the widget to match my site?

The widget inherits your page font by default. To customise colours and radii, override the CSS variables it exposes on the .bolmol-comments wrapper, for example --bmc-accent, --bmc-line, --bmc-bg, and --bmc-danger. All widget classes are prefixed with bmc-, so nothing leaks into your own stylesheet and the widget never overrides your global selectors.