mattermost/webapp/channels/src/components/edit_post/style.scss

// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
// See LICENSE.txt for license information.

.post--editing__wrapper {
    position: relative;

    textarea, #edit_textbox_placeholder {
        padding: 13px 16px 12px 16px;
        padding-right: 50px;
    }

    .edit-post-footer {
        &.has-error {
            color: rgb(var(--dnd-indicator-rgb));
        }
    }
}