Dear Sharkly One,
As someone with a decidedly Upper Austrian name (I checked), I wonder if there are names where agents/editors/publishers advise/demand the use of a pseudonym. On one hand, sure, the name's unique, but on the other hand, people might want to spell it without tripping up badly encoded software and/or non-native speakers. The same thing goes for overly long or unfortunate names.
On the legal end: Can such a thing be mandated? Is this a thing you/your slithery colleagues ever negotiated? Or am I just being completely ridiculous and this isn't a thing?
Yours truly, Ten-Characters-With-An-Umlaut
I've never heard of someone being asked to change their name for spelling sake. I'm sure it's happened, but I don't know of any specific examples. And honestly now, in this day and age, we're all used to umlauts and other festive punctuation:
Not to mention my favorite author name:
Jennifer 8 Lee
And it's not like Emily and Charlotte Brontë used nom de plums because of their surname.
As for demanding it, well, you're not being forced to sign a contract at gunpoint, so if a publisher insists on something you don't want, you just say "sayonara." Or as we like to spell it: