I do think there are two, or more than two LOL things to consider in this thread
1. OOC attachment to your slave or owner or companion or RP partner.
2. RP'ing the role of love slave or love Master instead of some other type of slave (this is not about OOC feelings)
Wanting to try to explore that role or dynamic of a love slave relationsihp isn't something roleplayers should necessarily shy away from IF they think they found the person with whom the OOC wants/needs/expectations/limits match.
The love slave dynamic could make a great story for both parties.
The problem is many equate this with a mirrored thing going on behind the scenes in IM's and that's not always so.
I think it could be quite challenging to play a slave who was convinced that she was the love slave of a man, but he didn't feel the same, he owned her but perhaps he scoffed at the concept of a love slave, or even loved another. Or a love slave who was sold to another, or whose owner died. The reverse could be fun, imagine a man who was convinced a certain slave was his love slave, and she was a good happy slave, and worked to please him, but it was another who lived in her heart or she simply isn't the type to love at all.
yes... those were challenging RP's and I don't necessarily recommend them after all.