bbPress.org

Copy the form-reply.php file into your child theme and remove this code for topic tags input on the reply form.

<?php if ( bbp_allow_topic_tags() && current_user_can( 'assign_topic_tags' ) ) : ?>

<?php do_action( 'bbp_theme_before_reply_form_tags' ); ?>

	<p>
	<label for="bbp_topic_tags"><?php esc_html_e( 'Tags:', 'bbpress' ); ?></label><br />
	<input type="text" value="<?php bbp_form_topic_tags(); ?>" size="40" name="bbp_topic_tags" id="bbp_topic_tags" <?php disabled( bbp_is_topic_spam() ); ?> />
	</p>

<?php do_action( 'bbp_theme_after_reply_form_tags' ); ?>

<?php endif; ?>

You can customize the content of the form using this CSS.

#bbpress-forums div.bbp-the-content-wrapper textarea.bbp-the-content {
    margin-top: 0;
    height: 210px;
}

The font is inherited from your theme.