“Come,” in start of a sentence

I think you're overanalysing this one. Obviously native speakers often make "slips" like this, especially in casual conversation or Q&A website comment posts.

In the case of X mistaken for Y, I imagine almost every competent native speaker would say for is "correct", but many if not most wouldn't see anything seriously "wrong" with as. A (probably, much smaller) number might not see much wrong with with.

This is an example of a comparatively minor slip. On a site like ELL, for example, many users are native speakers, and many aren't. As it happens, we have contextual information for the specific comment that sparked this question, making it highly likely that the writer is in fact a native speaker. But even if there were no such evidence, the fact of the usage itself would be no real reason to suppose otherwise.

This shouldn't be taken as a general principle for all "misused" prepositions, etc. Some errors are far less likely from native speakers, and far more likely to be seen as "giveaways" indicating "non-native".

Most of the examples sound fine, but these examples sound strange to me, and would make me believe the speaker is not native:

1. 06. One night in the middle of the night, I'm hearing dripping
This example sounds strange to me because progressives are rarely one-time events. If this is an unusual event, you might say "I heard dripping." However, if the speaker is about to switch into a direct, informal narrative in the historical present, it could sound perfectly natural, if informal, like this "One night, in the middle of the night, I'm hearing this dripping, so I get out of and look at the bathroom sink, and guess what I find there..." But in standard usage, I think "I heard" is preferable, because "One night" expects a past tense sentence.


2. 09. Tim, are you wanting any fruit?
"Do you want" or "Would you like" would sound much more natural to me.