Because Wordpress sucks.
More specifically, the way Wordpress handles markup sucks.
“But nfreader!” you’ll say, “Wordpress is great! It’s open source! There’s thousands of plugins! I love Wordpress and it loves you!”
To which I’ll say, “Yeah, but what if I just want to write a post without haggling with the editor?”
“You’re just doing it wrong, silly!”
Yeah, I’ve had enough. Hello Tumblr, will you be me friend?
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