Tumblr can be a bitch when it comes to formatting. I have a trick. You can highlight your writing and then click the “unordered list” button.
It will guarantee that line breaks are correct [I leave 1 empty bullet between each paragraph]. Before you post—rehighlight the text and then click the “unordered list” button to get rid of the bullets. The formatting should stay the way you want it.
Yeah, formatting on tumbr is a pain. I use markdown because those extra linebreaks I see everywhere on poetry would drive me nuts. I’d feel like I was leaving space for a teacher’s corrections…