vB5 Kullanıcıları için yatay postbit; Kodları Stiller ve Şablonlar >> İçerisinde, temanızın "css_additional.css" içerisine eklemeniz yeterli.

Bende yabancı bir kaynak sitede buldum. Kullanımı kolay.

/* YATAY POSTBIT */
.b-post .js-post__content-wrapper {
width: 100% !important;
float: none !important;
margin-left: 0 !important;
margin-right: 0 !important;
}
.b-post.b-post--first .js-post__content-wrapper .b-post__arrow {
border-bottom-color: #EBF4F9; /* Change to the first post background color if you changed the default */
}
.b-post .js-post__content-wrapper .b-post__arrow {
top: -10px;
left: 39px;
border-bottom: 10px solid #FFF; /* Change #FFF to the reply background color if you changed the default */
border-top: none;
border-right: 6px solid transparent;
border-left: 6px solid transparent;
}
.b-post .l-row .l-col__small--full {
padding-left: 0;
padding-right: 0 !important;
width: 100% !important;
float: none;
margin-left: 0;
margin-right: 0;
}
.b-post .b-userinfo__additional-info {
display: inline-block;
vertical-align: top;
margin-right: 10px;
}
.b-post .l-row .l-col__small--full .b-userinfo {
text-align: left;
padding: 10px;
}
.b-post .l-row .l-col__small--full .b-userinfo .b-avatar {
margin-right: 5px;
}
.b-post .l-row .l-col__small--full .b-userinfo .b-userinfo__details {
display: inline-block;
vertical-align: top;
}
.b-post .l-row .l-col__small--full .b-userinfo .b-userinfo__details .b-meter,
.b-post .l-row .l-col__small--full .b-userinfo .b-userinfo__details .b-userinfo__additional-info-block {
margin-top: 5px;
}
.b-post .l-row .l-col__small--full .b-userinfo .b-userinfo__details .b-userinfo__icons {
top: 10px;
bottom: auto;
left: auto;
right: 10px;
}
.b-post .l-row .l-col__small--full {
position: relative;
}
.b-sharing-menu {
position: absolute;
bottom: 10px;
right: 10px;
}
.l-desktop .b-post .b-userinfo__additional-info {
display: block;
}

.l-desktop .b-userinfo__additional-info-block {
position: absolute;
right: 10px;
top: 22px;
}

.l-desktop .b-post .b-sharing-menu {
bottom: -1px;
right: 17px;
}

.l-desktop .b-meter {
position: absolute;
right: 81px;
top: 10px;
}
.l-desktop .b-sharing-menu__item {
display: inline-block;
}
/* YATAY POSTBIT */