The trick is that gratitude and weariness are contradictory, which falls under the umbrella of what sarcasm provides; a way of expressing gratitude in such a way that weariness shows. The reaction of annoyance/​unpleasant surprise this causes on part of the receiver of sarcasm is anticipated by the speaker, and is considered a way of wounding them, which is why sarcasm can be used in arguments.
While both your intention and the conventional intention are both valid, the conventional intention is triggered, as the basic structure of expressing the spirit of one emotion with the letter of another is more commonly used, and thus more frequently recognized as such.
The trick is that gratitude and weariness are contradictory, which falls under the umbrella of what sarcasm provides; a way of expressing gratitude in such a way that weariness shows. The reaction of annoyance/​unpleasant surprise this causes on part of the receiver of sarcasm is anticipated by the speaker, and is considered a way of wounding them, which is why sarcasm can be used in arguments.
While both your intention and the conventional intention are both valid, the conventional intention is triggered, as the basic structure of expressing the spirit of one emotion with the letter of another is more commonly used, and thus more frequently recognized as such.
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