- 우리 교수님 성함은 심만찰이십니다.
- 우리 교수님 성함께서는 심만찰이십니다.
I saw the first sentence in my Korean textbook. I am wondering why don't we use 께서는 after 성함 as in the sentence #2.
When you say 우리 교수님 성함, you're omitting the possessive particle 의. (Which is totally fine, by the way.) Therefore, the topic particle should follow the actual subject - 성함 - not its possessive entity. So using 은 is correct here.
Think of it like this. Your professor is respectable (A teacher/mentor is one of the three people who deserves the most respect from you Technically speaking, it's never OK to not use 께서는), so you use the honorific form of name. However, a name is not a respectable entity; it's just a thing. Hence you do not use the honorific 께서는.
This kind of "honorific precedence" creates some confusing situations for even native speakers (although not many people actually care that much). For instance, "I told my professor the truth" translates to 나는 내 교수님께 그 사실을 말해 드렸다 while "My professor told me the truth" translates to 내 교수님께서 내게 그 사실을 말씀해주셨다. "말" comes from the speaker and therefore follows the subject, but "해주다" is given to the receiver and therefore follows the object. In reality we tend to just honorify everything (i.e. 말씀 드렸다) but technically we're not supposed to show respect to our own speech, but rather to the action that the respectable person is receiving.
Please take it with a grain of salt since I'm only sharing my experience as a native speaker, not a formally trained expert in Korean grammar.
P.S. When you say the name of someone older than you, you must say 심 만자 찰자 입니다. While this rule may not be kept so strictly on a daily basis, I find this to still hold true in very formal settings.
께서(는) is used on people who deserves a VERY HIGH respect.
성함(Family name) is a name, not a person, so it does not deserve any respect.
Even though you are using 교수님, it is OK to use 이/가/은/는 instead of 께서(는), since, whether a professor deserves a very high respect, it depends on how you think.
We usually use 께서는 when:
The person CLEARLY deserves a very high respect. (i.e. President, Prime Minister)
The person is the SENIOR of your family or any other entities of yourself (or your friend's sometimes)
Correct me if I am wrong.