Another test with a text in English, which is maybe more fair (although Mistral is a French company ;-). This image is from Parliamentary debates of the parliament of New Zealand in 1854-55:
Here's the output of the first paragraph, with mistakes in brackets:
> drafts would be laid on the table, and a long discussion would ensue; whereas a Committee would be able to frame a document which, with perhaps a few verbal emundations [emendations], would be adopted; the time of the House would thus be saved, and its business expected [expedited]. With regard to the question of the comparative advantages of The-day [Tuesday]* and Friday, he should vote for the amendment, on the principle that the wishes of members from a distance should be considered on all sensations [occasions] where a principle would not be compromised or the convenience of the House interfered with. He hoped the honourable member for the Town of Christchurch would adopt the suggestion he (Mr. Forssith [Forsaith]) had thrown out and said [add] to his motion the names of a Committee.*
Some mistakes are minor (emnundations/emendations or Forssith/Forsaith), but others are very bad, because they are unpredictable and don't correspond to any pattern, and therefore can be very hard to spot: sensations instead of occasions, or expected in lieu of expedited... That last one really changes the meaning of the sentence.
https://i.imgur.com/1uVAWx9.png
Here's the output of the first paragraph, with mistakes in brackets:
> drafts would be laid on the table, and a long discussion would ensue; whereas a Committee would be able to frame a document which, with perhaps a few verbal emundations [emendations], would be adopted; the time of the House would thus be saved, and its business expected [expedited]. With regard to the question of the comparative advantages of The-day [Tuesday]* and Friday, he should vote for the amendment, on the principle that the wishes of members from a distance should be considered on all sensations [occasions] where a principle would not be compromised or the convenience of the House interfered with. He hoped the honourable member for the Town of Christchurch would adopt the suggestion he (Mr. Forssith [Forsaith]) had thrown out and said [add] to his motion the names of a Committee.*
Some mistakes are minor (emnundations/emendations or Forssith/Forsaith), but others are very bad, because they are unpredictable and don't correspond to any pattern, and therefore can be very hard to spot: sensations instead of occasions, or expected in lieu of expedited... That last one really changes the meaning of the sentence.