Hey so just a heads up, I made a few more changes that I quite like (again, for the red theme, tweak appropriately for the default green theme), so thought I'd just update you.

This changes the main feed quite a bit, adding a bit more of a card-like design to posts, though I have done my best to make sure there isn't too much white-space from this change, I just feel it looks a bit more modern, but again, feel free not to use it :)

It also, and this is my favorite change, changes the title color of any post you've visited, something that I feel is basic but for some reason Lemmy didn't have before. So now any posts you've visited before will be a light-gray color instead. Hope you find some value here.

.container-lg {
    max-width: 1600px;
}
.col-md-8 {
    max-width: 80%;
    flex: 0 0 80%;
}
.col-md-4 {
    max-width: 20%;
    flex: 0 0 20%;
}
.col-sm-2 {
    max-width: 10%;
    flex: 0 0 10%;
}
.col-sm-9 {
    margin-left: 5px;
    max-width: 80%;
    flex: 0 0 80%;
}
.post-listing {
    border: 1px solid rgba(34,34,34,.125);
    /*border-bottom: 0px;*/
    border-color: #c80000;
    border-radius: 5px;
    margin-bottom: 8px;
    padding-top: 10px;
    background-color: #fff;
    transition: all .2s;
    box-shadow: 2px 2px 1px #c80000;
}

hr {
    display: none;
}
.border-top {
    border-top: 1px solid rgba(34,34,34,.125)!important;
}
.border-light {
    border-color: #e4e4e5!important;
}
body {
    background-color: #ecf0f1;
}
.navbar {
    background-color: #fff;
}
.card {
    background-color: #fff;
    box-shadow: 2px 2px 1px #c80000;
}
.col-12 .card {
    box-shadow: none;
}
.comments {
    padding-left: 10px;
    background-color: #fff;
}
a:visited .d-inline-block {
    color:#d6d7d9!important;
}
.my-2 {
    margin-bottom: 0px!important;
}