I personally think that as long as it's a genuine question and is phrased correctly without any malicious intent then it's okay. Questions like sexual health or sexual personal problems are natural and common issues for adults to ask for help.

However if you're question/answer involves you attaching pictures of nude people or pictures of specific body parts that shouldn't be seen in a public platform like this, then just don't do it. 

Also as far as I know adding #nsfw as a tag or category in other Steem platforms hide the image visually, if you are planning to ask a nsfw question in here then maybe you should try adding #nsfw as one of the categories too.