pp 152 and 294, Kuldeeph Singh's Linear Algebra: Step by Step (2013) illustrates Triangle Inequality. But without referring to Triangle Inequality at all, how to picture Reverse Triangle Inequality for all $\mathbf{a,b} \in C^n$? I don't want proofs or rigour.
The intuition is that the inequality is equality whenever there's no cancellation happening. I'll keep this in the reals but the idea generalises. Suppose that $a,b > 0$. Then \begin{equation} | |a| - |b| | = |a - b| \end{equation} whereas, if $a > 0 > b$, then \begin{align} | |a| - |b| | &= | a + b | \leq \max\{|a|, |b|\} \leq \max\{a, -b\} \leq \max\{a, -b\} + \min\{-b, a\} = a - b \\ &= |a - b| \end{align}
If you want to think more geometrically then $|a - b|$ is the size of the vector from $b$ to $a$ which is minimised when they're both pointing in the same direction and, at that minimum, is the LHS above. When they're not pointing in the same direction then $|a - b|$ is bigger but $||a| - |b||$ stays the same size (as it doesn't care about the angle between $a$ and $b$).