mar'is ayin on issurei derabbanan: non-dairy creamer with meat

There is another gem buried in this machlokes Tosfos and Ramban (see yesterday’s post). While the issue of lifnei iveir may or may not apply to issurei derabbanan, it seems that none of the Rishonim had a problem with the sugya's assumption that mar’is ayin applies to issurei derabbanan. R’ Shimon ben Elazar prohibits renting a filed to a kusi; since the field is known to belong to a Jew it gives the mar’is ayin appearance that a Jew is working on chol hamoed, which according to Tosfos is an issur derabbanan, and even Ramban only is forced to say melacha on chol hamoed is an issur d’oraysa because he held an issur derbbanan is incompatible with lifnei iveir, not because it was incompatible with mar’is ayin. The point is notable because of a psak of the Rama in hilchos basar b’chalav. Rama (Y.D. 87) writes that if non-dairy creamer made from nuts is served with a fleishig meal of beef, the nuts should be placed next to the creamer container to avoid a problem of mar’is ayin. However, if served with a chicken meal, which is only basar b’chalav derabbanan, there is no concern for mar’is ayin (take a look in poskim for practical applications like caterers serving non-dairy creamer in serving cups with no label to indicate it is not real milk). The Shach attacks the Rama – who says mar’is ayin does not apply to issurei derabbanan?! While the Shach does not specifically reference this sugya, he brings other proofs and writes in general that this principle is supported from many places in shas. In defense of the Rama, one can perhaps distinguish between mar’is ayin on a public act and something like a meal which takes place in a private setting. While the gemara often quotes Rav’s dictum “kol ha’asur m’shum mar’is ayin afilu b’chadrei chadarim hu assur”, rejecting such a distinction, Tosfos (Kesubos 60a) writes that Rav’s principle applies only where the potential issur is an issur d’oraysa. It is also worth noting that the RIF (see Ran to Beitzah daf 9) may reject Rav completely, as is the opinion of the Yerushalmi (as noted by the Gilyon in a recent daf in Shabbos – I did not get a chance to track down where I saw this, so if anyone else is learning the daf yerushalmi and recalls where it is, please remind me!)