William Shatner is always up for a a good pop culture debate. For example, he'll be the first to explain to you on Twitter why Star Trek is better than Star Wars. Of course, he's a guy who would know because Captain Kirk knows more about the galaxy far, far, away than you might expect. Shatner ended up schooling somebody on Legends canon during a conversation about the sexuality of various 1970s big screen space heroes. Because that's always where these conversations end up.
The conversation started following rumors that a new Star Trek spinoff series might include a version of James T. Kirk that was bisexual. William Shatner says he's fine with such a decision if it's made, but as one might expect, the conversation didn't end there. Shatner explained that fans could even choose to read his version of the character that way, and he'd be ok with it. This led one fan to remark that Mark Hamill had said similar things about Luke Skywalker. Somebody responded that since Jedi are basically monks, relationships were never important to Luke Skywalker. And then William Shatner had to go and burst that bubble.
While the original batch of Star Wars books might no longer be officially canon, they do still exist. And that means that at least one version of Luke Skywalker did have a relationship. Of course, Luke Skywalker of the movie series seemingly didn't do the same as technically those stories are not officially part of the storyline. At the same time, many aspects of the Legends canon have been adapted if not borrowed completely for the modern stories. So the possibility that Luke Skywalker did have a relationship, or more than one is certainly possible.
Needless to say, the fact that William Shatner is breaking out Star Wars trivia is blowing some minds. On the one hand, I suppose the fun that William Shatner has at the expense of Star Wars might make one assume he doesn't care that much. But then again, it helps to know you're enemy.
Of course, a lot of people are familiar with Mara Jade, at least by name. She was an incredibly popular character when the Legends books were all there were for new Star Wars, and many would like to see the character become part of the new canon in the same way Grand Admiral Thrawn and others have made the jump from Legends to modern canon.
The Star Wars vs. Star Trek battle will likely go on forever. As with most pop culture smackdowns they're not all that important and hopefully people have fun with them more than anything. And if you do have questions about the lore of either franchise you can apparently ask William Shatner. It's unclear just how much Mark Hamill knows about the history of Star Trek though.