The reason it only somtimes works for me is when the charaters are anthros and I also only read the text.
To chime in on this recurring conversation I think this is really important.
Remember that we are several layers deep away from actual sexual acts.
1.We're an outside observer, not participating.
2. We're looking at fiction, not real characters.
3. We're looking at what are basically cartoons, with little relationship to real life.
4. It'd all in text!
Relating what gets you going as a third party observer in a fictionalized, unrealistic, text based environment to your real-life sexuality/interests/fetishes is really just an excessive in futility.
For example, I like drider/spider girl scenes, especially ones with egging.
But outside of text? Eff no. Eggs being shoved into someone is horrific looking imo, even cartoonified. And I would probably straight commit sudoku before going through it in real life...
All to say this is a silly conversation. But an interesting one! That will probably repeat itself 1000 more times!