I can think of some examples, but what can be an outline of the proof?
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1$\begingroup$ A continuous preference relation can always be represented by a continuous function. However, It can also be represented bu other (nom-continuous) functions. $\endgroup$ – BB King Oct 16 '18 at 14:55
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Indeed you are correct that a continuous utility function can be represented by a discontinuous function. However, I am not sure what you mean by proof beyond an example; an example is a proof of this fact.
For completeness, here is an example we can take $\succeq\,\subset \mathbb R \times \mathbb R$ to reflect the usual ordering (i.e., $x \succeq y$ iff $x \geq y$). Clearly this is a continuous ordering as its contour sets are intervals. The utility function $$ U(x) = \begin{cases} x &\text{ if } x < 4 \\ x + 1 &\text{ if } x \geq 4 \end{cases} $$ is discontinuous, but represents $\succeq$.
Any such function is necessarily have a continuous representation as well.
