That way, neither themes nor CSS will lead to the colour accidentally being overridden.

this is not true. this example style should disprove your case: 

/* color links */
a, a font { color: #457; background: #eee; text-decoration: none; }
a:hover { color: #eee; background: #457; }

/* override <font>...</font> tags */
font, b, strong { color: #457; background: transparent; }

[download]
there are multiple ways to override the font tags in your example. my browser does not display your text in red, as you specified, as all font tags are overridden by a user-supplied style.

as to

a representation that would be completely and entirely unmistakable under any circumstances
... you'll have to aim a little higher ;-)

~Particle *accelerates*

In reply to Re^4: Filtering potentially dangerous URI schemas in <a href="..."> by particle
in thread Filtering potentially dangerous URI schemas in <a href="..."> by IlyaM

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