[@ArenaSnow] I view people who require a certain gender to RP a little differently myself and consider them more offensive. I see it as a kind of [url=https://en.wikipedia.org/wiki/Metagaming]Metagaming[/url]. Pretty much the only thing that "triggers" me is cheating, and metagaming is most often used for cheating, but usually it's because the RPer has limited skills and sees everyone else as having the same limited skills. However, it can easily get even creepier than that (and typically does) depending on what is the requiring person wants to RP. 

Like, instead of coming out and saying "Cyber with me!" its somewhat implied that they're thinking "I'll just pretend you are your character, and fap to you directly" like they don't know that we know that's what they're doing.

Regarding 18+ I understand that it's the site's policy that Mature and 18+ are meant to be largely interchangeable ([url=https://www.roleplayerguild.com/topics/58632-1x1-interest-check-guidelines-for-mature-content/ooc]I had to check to be certain[/url]), but they still imply different things based on how they're used by the people (and types of people) who prefer one over the other. As far as I can tell the difference seems to be that "Mature" tag means the content requires a mature set of sensibilities, while "18+" tag means players need to be interested in "mature" content. 

The distinction comes into play because being interested in mature content does not make you mature.

Regarding age itself, to me personally, if a body doesn't have 5 or more years experience being an adult (23 or older), then I don't really consider them one. After all, an 18 year old adult generally has 18 years experience being a kid, and no years of experience being an adult.