kesiva k'dibbur

R' Akiva Eiger (Shut 30) raises the question whether writing counts l'halacha as dibur or not, e.g. if one wrote "ha'yom yom echad ba'omer" instead of saying the words, is one yotzei?   (The question may go back to a machlokes Tanaim in Mechilta -- see this post).  

R' Akiva Eiger brings proof from the following sugya: 

The Mishna in Megillah (17) has a din:  הָיָה כּוֹתְבָהּ, דּוֹרְשָׁהּ וּמַגִּיהָהּ, אִם כִּוֵּון לִבּוֹ — יָצָא, וְאִם לָאו — לֹא יָצָא

The gemara (18b) asks what the case in the Mishna is.  If the baal koreh says pasuk by pasuk aloud and then writes it, even if he has kavanah he should not be yotzei, as when he says the pasuk he is not reading from a text.  And even if he writes the pasuk first and then reads it, he still should not be yotzei, as the halacha requires reading megillah from a *completed* text.  Answers the gemara:

אֶלָּא: דְּמַנְּחָה מְגִילָּה קַמֵּיהּ וְקָרֵי (לַהּ) מִינַּהּ פְּסוּקָא פְּסוּקָא וְכָתַב לָהּ. 

The case is that the baal koreh had a complete megillah in front of him, and he read the pasuk from that megillah, and then wrote it into the text he was working on.

Why does the gemara needs to add that the baal koreh read the pasuk and then wrote it to be yotzei?  The first case in the Mishna is simply הָיָה כּוֹתְבָהּ -- someone was writing a text.  Maybe the case is that the sofer was copying from a completed megillah and is yotzei by writing?

QED, says R' Akiva Eiger, that in order to be yotzei kri'as ha'megillah you need to READ the text, not just WRITE the text.  Kesiva is not the same as dibur.

Or maybe you can argue.  R' Simcha Elberg points out that there are 2 dinim in kri'as ha'megillah: 1) a din kri'ah; 2) a kiyum of pirsumei nisa.  (See this post where I used this same idea to explain shitas haTos that you say she'hechiyanu on the kri'ah by day and by night).  The gemara (18a) writes that we don't know what some of the words mean, but we are yotzei anyway because the reading of megillah accomplishes pirsumei nisa.  

If so, it could be that kesiva is the same as dibur, but the chiyuv of megilah requires not only dibur, but specifically a dibur that accomplishes pirsum -- that is noticable, that people are aware of.  The scratching of the pen as the sofer writes fails to accomplish that.