After I figured it out, I found a couple of commentaries in Portuguese that mentioned it.

Though they didn’t draw much meaning from the structure, except Javier Pikasa’s Teologia de Mateus (Edições Paulinas, 1984, 2nd ed.), translated from the Italian.

In the structure as I see it, 8:18-22, 9:9-13 (with vv. 14-17) and 9:35-38 are emphasized after each of the three series of three miracles. Each of these texts deals in some fashion with discipleship: (1) two offer to follow Jesus and are rebuffed; (2) Jesus calls one to follow and he accepts; (3) Jesus has compassion on the multitude, who are as sheep without a shepherd — no one to follow.

The focus falls on the calling of Matthew, the one who hears and accepts the call to follow Jesus. The question on fasting explains the nature of this Lord/servant relationship, different than anything that has gone before it. Truly, the Lord is doing a new thing in Israel!

Matthew 8:1—9:38

 A. Heals a leper, 8:1-4.
 B. Heals a Roman official's servant, 8:5-13.
 C. Heals Peter's mother-in-law and many, 8:14-17.
    D. Two offers to follow, 8:18-22
 AA. Calms the storm, 8:23-27.
 BB. Cures two demon-possessed, 8:28-34.
 CC. Cures a paralyzed man, 9:1-8.
     DD. Jesus calls Matthew, 9:9-13.
         E. Question on fasting, 9:14-17.
 AAA. Cures a woman and child, 9:18-26.
 BBB. Cures two blind men, 9:27-31.
 CCC. Cures mute possessed of demon, 9:32-34.
      DDD. Compassion for multitude, 9:35-38.

What do you think?