So apologizers use words that are hard to produce (but not hard to understand), and this strategy works!
Link: doi.org/10.1111/bjop...

Apologies with long words were perceived as more apologetic than those with shorter words that were matched for frequency. In contrast, word frequency did not influence how apologetic the sentence seemed.

But is this strategy effective? To test that, participants were presented with triads of apologies that had the same meaning but differed in word length or word frequency. The triad sentences appeared in random order and participants ranked them from most to least apologetic.

Apology tweets of 25 celebrities and 25 non-celebrities were compared to other tweets by the same users. Apology tweets had longer words! In contrast, they didn’t have more infrequent words.

Longer words and infrequent words are harder to produce, so these might be good candidates for apologies. But infrequent words are also harder to understand, so they will burden the addressee. A sophisticated apologizer might then use longer words but not infrequent words.

They make the apology costly by investing time, money, or effort (e.g., traveling specifically to apologize to a friend vs apologizing to them the next time you happen to meet them).
What about making the apology itself more costly by producing words that are harder to produce?

Apologies are cheap – anyone can apologize regardless of whether they’re sorry. So how do apologizers convince the recipients that they are sincere?