I'm not sure what you mean. Unicode doesn't have fonts. It has code blocks and code points. Fonts are how your computer chooses to render those code points.
On my browser, I don't see anything special about C, H, P, or Q on the page that you link to. They look similar to all of the other double-struck characters. Perhaps the font you are using is wonky?
It says that the mathematical blackboard-bold symbols appeared in Unicode first, and the full set of double-struck characters appeared later. That includes C (complex), H (quaternions), etc. It's possible that your font is rendering those as actual-bold (for which blackboard-bold was supposed to be a hand-written substitute).
On my browser, I don't see anything special about C, H, P, or Q on the page that you link to. They look similar to all of the other double-struck characters. Perhaps the font you are using is wonky?
However, I did find this note on stackexchange:
https://stackoverflow.com/questions/28012644/whatever-happen...
It says that the mathematical blackboard-bold symbols appeared in Unicode first, and the full set of double-struck characters appeared later. That includes C (complex), H (quaternions), etc. It's possible that your font is rendering those as actual-bold (for which blackboard-bold was supposed to be a hand-written substitute).