I’m writing this piece as i have gotten rather tired of explaining this point over and over. Writing an article about it saves me time.
The form of reasoning goes something like this:
1. This person uses some other spelling than the standard one for a word.
Therefore, 2. This person does not know how to spell the word.
It shud be relatively easy to see that this does not follow. Obviously, if one is familiar with spelling reform ideas, then that makes for easy counter-examples. But even people who have not thought/read about spelling reforms shud be somewhat familiar with familiar use of non-standard spellings in their native language. For instance, when speed is important, people may use alternative spellings becus they are shorter. For instance, using y for yes. Altho someone might see this as using abbreviations and not non-standard spellings. It can be rather difficult to distinguish between the two. Is becus an abbreviation that doesn’t count? How about ‘cus?
Another realm of counter-examples is when people deliberately ‘misspell’ a word for some other purpose, e.g. humor (making a pun), or to signal dialect (writing aks instead of ask), or murika instead of America thereby noting that the word is pronounced like that by many americans. Clearly, many people who do these things are aware of the standard spelling.
As an inductive inference?
In the above, i assumed that the argument was deductive, as in, the conclusion was supposed to follow with necessity by the reasoner. However, one might think of it as a probabilistic inference. Does it fare much better this way? Sort of. Certainly, sometimes people do try to write the standard spelling of some word, but for some reason write something else than that. This can be for many reasons: hitting the wrong key on the keyboard, being distracted at the moment of typing (typically results in one typing the word that was said to one) or just genuinely making a mistake (genuinely making a mistake! :D) becus one was wrong about how the word is spelled in the standard spelling.
Generally, tho, there are some patterns that one can use to make better guesses at whether people really did make a mistake becus they didn’t know the correct spelling, or something else is the case. There are lists of commonly misspelled words (example), if a person used one of the common but nonstandard spellings, then it increases the probability that it was a mistake. How does one spot typos? Usually, the character that is part of the nonstandard pattern is located near the intended one. This produces things like I luke you instead of I like you. Finally, the function words of a language are rarely misspelled becus they occur in high frequency. For that exact reason they also have the poorest spellings. If someone uses nonstandard spellings for such words, then that increases the probability that it is on purpose. Examples of this are words like could should would you I which might be written cud shud wud u i for various reasons.
Under which conditions wud the inference actually work deductively?
Perhaps if one added some extra premises then the inference wud work. Any candidates? Yes. Adding something like: Every person is always trying to use the standard spelling for every word. Implausible? Very! And it isn’t even enuf. There remains the possibilities of being distracted and hitting the wrong keys, and perhaps some other things i haven’t thought of.
Is it really a modal fallacy?
Yes.
Modal logic is that branch of logic which studies logical relations involving modalities. Modalities are ways, so to speak, in which propositions can be true or false. The most commonly studied modalities are necessity and possibility, which are modalities because some propositions are necessarily true/false and others are possibly true/false. (source)
Name for the fallacy?
Can’t think of anything good. It shud be short and relevant. Things like the anti language reformist fallacy is not short but at least it’s descriptive.