Shalom R' Dino,

It's great to hear from you!

1)

a) This is a fantastic question! You may know that there is a lengthy Magen Avraham (Orach Chayim 156) which addresses an assortment of laws -- including Lashon ha'Ra -- which the Shulchan Aruch omitted.

b) I believe that some might be tempted to suggest that the reason is because those omitted laws relate to character traits and emotions, as opposed to the topics of typical Simanim in Shulchan Aruch which are comprised of straightforward laws. But I don't suspect that is the answer, because other laws related to "Midos" are in fact included in the Shulchan Aruch (for example, Ona'as Devarim).

c) Instead, I imagine that the simplest explanation for why the Shulchan Aruch omitted these laws is that they are rather general in nature. In other words, the Shulchan Aruch, like his predecessor the Tur, arranged each set of Halachos in order of their application to life circumstances. For example, Orach Chayim deals with Berachos, Tefilah, Shabbos, Yom Tov, etc.; Yoreh Deah deals with Kashrus, idolatry, Talmud Torah, etc. But it can be argued that laws which apply generally, important as they are, were excluded from the legal code precisely because they do not necessarily fit neatly into one Siman or another.

d) This, by the way, would not be the case for Ona'as Devarim, since that naturally occupies a space -- in Shulchan Aruch, as in Shas -- next to the laws of Ona'as Mamon. Nevertheless, this theory does still leave a question unanswered, namely, why didn't the Shulchan Aruch simply create a new Siman for these generally applicable laws?

2)

a) You are suggesting a very interesting idea. I believe, however, that we would have to hesitate before necessarily accepting this as the definitive reason. We would need to consider several other Halachos, which the Shulchan Aruch does include, even though in those cases it would also be better not to tell people (so that they shoud not be Meizidin).

b) For example, Orach Chayim 339:3 teaches us not to clap on Shabbos, even though the Rema points out that it is better not to object when people do so since we prefer that they should not do it b'Meizid. Similarly, Orach Chayim 428:2 teaches that we should not instruct women to refrain from eating until the end of the day on Erev Yom Kippur, because it is better that they should not do it b'Meizid.

May you continue to attain greatness in Torah and Yir'as Shamayim!

Warmly,

Yishai Rasowsky