ONLY in the CONTEXT of a BELIEF SYSTEM which would deem it as such.
I think this is actually largely dependent on what sexual talks you are engaged in and who's discussing such.
If it is between two people, happily in love about to get into a relationship, then it isn't bad if they're discussing their sexualities, how they like to have sex and all.
But if it is between two young people with no intent of getting married, then I think it is immoral
Firstly, It actually depends on your age. It's not advisable for very young kids to engage in such talks as it may lead them to premarital sex at their very early stage. This is why sex education is sometimes very important in the lives of young kids.
Secondly, it depends on whom you are conversing with. There is nothing bad if you engage in sexual talks with your wife or lover because it creates a free sense of interaction that has to do with one's weaknesses and strengths before or after sex. It enables the wife to explain some cool sex styles or positions she loves best and this also applies to the husband. As we all know that a good sex will also strengthen the bond of the relationship.
Lastly, it depends on your intentions. I don't think there is anything bad in asking questions about ambiguous things you find difficult to comprehend. You can meet with an expert and converse with such person and you will be told important things you need to know about sex.
Thanks for reading and I hope this helps.
Sexual curiosity is part of any healthy relationship. To actually not discuss it is like intentionally missing something important in your human relationship. Sex goes beyond the physical contact. There's actually more harm in avoiding the subject because it closes up other topics like contraceptives, family planning, and sexual habits and attitudes of your partner.