I wouldn't say it's obligatory, especially since the poster already was aware of not assuming gender by using "he/she" (though I know some people identify as neither of those). I do prefer singular they; it's very natural and yes, it's been around in English for a long time.
The use of their / they refering a single person doesn't come naturally to me as english is my 2nd language and we're taught its plural. (it can indeed be used as "third person plural singular" according to oxford dict.)
Since its the "least bad" (to my ears) of the gender-neutral pronouns on the wiki page I'll try to use the "they/their" instead.
Today's post is way more in-depth. Good follow-up indeed.