fix: make sure that transparent stuff can't have borders

src/scss/_definitions.scss

@@ -104,6 +104,12 @@ $screen-xxl-min: 1600px;
   border: $border-size solid rgba(0, 0, 0, 0.3)
 }
 
+@mixin prefer-no-borders() {
+  &:not(:hover) {
+    border-color:transparent;
+  }
+}
+
 @mixin border-radius($border-radius) {
   border-radius: $border-radius $border-radius $border-radius $border-radius;
 }

src/scss/components/_buttons.scss

@@ -105,12 +105,14 @@ $button_small: $lineheight_quarter;
 
 .btn-navbar {
     @include button-fullcontrol(transparent, rgba(0,0,0,0.1), $color-font-light);
+    @include prefer-no-borders();
     padding-left: $button_small;
     padding-right: $button_small;
 }
 
 .btn-readmore {
   @include button-fullcontrol(transparent, darken($color-background-alt, 7.5%), $color-primary);
+  @include prefer-no-borders();
 }
 
 // BUTTONS GROUPS
@@ -168,7 +170,10 @@ ul.breadcrumb, ol.breadcrumb, .breadcrumb {
 
 .btn, a.btn, .btn.btn, .badge, .chip, a.chip, a.badge, .label, a.label, label.label {
     @each $name, $color in list-colors() {
-        &-#{$name} { @include button-color(get-color($name)); }
+        &-#{$name} {
+          @include button-color(get-color($name));
+          @include borders();
+        }
     }
     &-link {
       @include button-color(transparent);

src/scss/components/_cards.scss

@@ -127,6 +127,7 @@ $card-smallpad: $lineheight_half;
 
             @include shape-style($lineheight_half);
             @include button-hover();
+            @include prefer-no-borders();
 
             strong {
               font-weight: 900;