I think this is exactly the argument mentioned long ago in the בכור case, that the caf and vav are so close to each other but not touching. [posts given at end of this blog]
The opinions in regard בכור that say that it is kosher as is, so no need/care what a tinok will read. Accordingly here, they will say since the yud and nun are touching and they are a kosher zadi, we are not concerned what a tinok may read.
[I don't think anybody is concerned of the regel of the yud - as a cause of a shinuy tzura of the zadi].
The opinions mentioned in regard to בכור that say that although the letters are not touching, still the wrong conception in the eyes of a tinok cause them to be considered another letter [in that case - mem], will say here the same - we must ask a tinok what does he read חמץ או חמין???
See The word בכור that the caf and vav are very close to another
and The word בכור that the caf and vav are very close to another #2