How do illogical proofs or answers “feel” to mathematicians?

My answer to a question on Quora: How do illogical proofs or answers “feel” to mathematicians? Is it the same as a somewhat educated layman hearing grammatical mistakes or messy constructions in a sentence? 

Is it the same as a somewhat educated layman hearing grammatical mistakes or messy constructions in in a sentence?

Many thanks for this comparison. Yes, I think it is the same. Some kind of errors or flaws in arguments, say, in a PhD student’s work, are seen at the first glance at the text: they stand out of the text, they appear to be distinctive and crisp while the rest of the text is still blurred, they shout at me. Just today I had a conversation with my colleague, we co-supervise the same student together — my colleague had exactly the same experience.