This is something that applies to every story but for some reason I tend to see it more in fanfictions. That's spacing.

Not skipping spaces between words, the spacing between paragraphs. This isn't something everyone can control automatically because for some reason writing on a phone gives different spacing than writing on a computer. For example:

Phone Spacing

"She has blue in her hair!"
"What do you mean?"
"Look at that, Clara, your daughter has a few blue streaks in her hair," the doctor, a fellow co-worker of Clara (L/n), claimed, "She might have a mutation, Clara." 

Computer Spacing

"Nice job kid."

"Thanks, I mean I could've stuck the landing a little better. It's just a new suit. It's nothing Mr. Stark it's perfect-"

"Yeah we don't really need to start a conversation."

"Cap-Captain, big fan. I'm Spider-Man."

"Yeah we'll talk about it later."

"Hey everyone."

"Yeah, good job."

See, phone spacing tends to be closer together, more bunched. It isn't necessarily annoying it just makes things a bit more difficult to read and it makes your chapters seem shorter than they actually are. 

There's an easy fix to this that only requires a bit more effort. When writing from your phone, tap the enter button twice so it has correct spacing and looks like it will on a computer. This will spread it out, make it easier to read, and make it more neat in general.

Hope you enjoyed! Feel free to request and ask questions! Love you all! Byeee!

~ Lydia