Harry read, and reread the letter at least a dozen times, for two reasons. One, to ensure he’d given no information away that might in some way reveal where Sirius was, or draw attention to any of the Order’s business unnecessarily - he’d lingered for a long time on mentioning Hagrid, but erred on the side of: why would he hide the fact that Hagrid wasn’t there? Umbridge wasn’t blind, she could see he wasn’t there! And two, to ensure he’d given Sirius no excuse to be reckless and try to speak to them through the fireplace. They’d been lucky last time, that Umbridge hadn’t actually managed to grab hold of him, and Harry would lose his actual shit if he pulled a stunt like that again. He read it one last time and added one small detail (two x’s at the end of "love Harry’), before swinging himself out of bed, satisfied.