Encoding a message to a point of curve y^2=x^3+7 and Bitcoin Core
In ECDSA, the message is never encoded as a point in the elliptic curve. Signing in ECDSA loosely works like this:

$$
\begin{align*}
k &amp;= \text{random}(0, n) \\
(x, \_) &amp;= k \cdot G \\
r &amp;= x \bmod n \\
s &amp;= k^{-1}(H(m) + r \alpha) \bmod n
\end{align*}
$$

$r$ and $s$ are the signature, and as you can see $H(m)$ is only ever used as an element of the integers modulo $n$, the order of the generator point $G$ (and $\alpha$ is the private key). Therefore, $H(m)$ is never treated as a point, and thus never needs to be encoded into one.