Personally, your proposed syntax feels too busy for me to be used as an inline notation. And I think it would be beneficial if the link type notation would be part of the link itself, and not be placed outside of the link. Also, I’m not sure if link-specific color & thickness specifications are really needed. Personally, I’d want a semantically named link type (like “supports” or “refutes”) to always use the same visual appearance (e.g. thick green or red, respectively). Attraction (aka “weight”), however, seems useful and could be used to style the thickness property of the link’s edge/arrow.
Personally I’d prefer a key:value-style syntax inside the link (proposed here):
[[supports::LINK_ID]]
[[evidenced by::weight:10::LINK_ID]]
If really needed, this generic system could be also used to add key:value types like color:..., thickness:... & attraction:....