Is there a general principle for how we treat a י"א = יש אומרים (yesh omrim, "some say") cited in the Shulchan Aruch for the purposes of determining halacha? If not, are there examples of two halachos where we use different approaches towards a י"א (e.g. following one but not the other, treating one as going l'chumra and one as going l'kula, etc.)?
Synopsized from Yad Malachi (K'lalei Haposkim - HSh"' VRM"' #13,14,16,17):
- When the Shulchan Aruch quotes an unattributed halacha followed by one introduced with the words "yesh om'rim" it indicates that the unattributed opinion is authoritative.
- This is [almost] universally agreed despite the fact that occasionally the conclusion of Beis Yosef coincides with an opinion under the heading "yesh om'rim" and not with the unattributed one that preceded it.
- When it says "yesh om'rim X v'yesh om'rim Y" it is deciding in favor of the second opinion.
- Some interpret such a formulation as non-determinative.
- When it introduces an opinion with "yesh om'rim" and follows that with an opinion beginning "v'yesh mi she'omer" the first one is authoritative.
- Some disagree and therefore this rule is unreliable.