Looks better without Segoe UI on Windows.

static/css/bootstrap.css

@@ -268,7 +268,7 @@ html {
   -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
 }
 body {
-  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
+  font-family: -apple-system, BlinkMacSystemFont, Helvetica, Arial, sans-serif;
   font-size: 14px;
   line-height: 1.42857143;
   color: #333333;
@@ -490,7 +490,7 @@ small,
 mark,
 .mark {
   background-color: #fcf8e3;
-  padding: .2em;
+  padding: 0.2em;
 }
 .text-left {
   text-align: left;
@@ -793,13 +793,71 @@ pre code {
   margin-left: -15px;
   margin-right: -15px;
 }
-.col-xs-1, .col-sm-1, .col-md-1, .col-lg-1, .col-xs-2, .col-sm-2, .col-md-2, .col-lg-2, .col-xs-3, .col-sm-3, .col-md-3, .col-lg-3, .col-xs-4, .col-sm-4, .col-md-4, .col-lg-4, .col-xs-5, .col-sm-5, .col-md-5, .col-lg-5, .col-xs-6, .col-sm-6, .col-md-6, .col-lg-6, .col-xs-7, .col-sm-7, .col-md-7, .col-lg-7, .col-xs-8, .col-sm-8, .col-md-8, .col-lg-8, .col-xs-9, .col-sm-9, .col-md-9, .col-lg-9, .col-xs-10, .col-sm-10, .col-md-10, .col-lg-10, .col-xs-11, .col-sm-11, .col-md-11, .col-lg-11, .col-xs-12, .col-sm-12, .col-md-12, .col-lg-12 {
+.col-xs-1,
+.col-sm-1,
+.col-md-1,
+.col-lg-1,
+.col-xs-2,
+.col-sm-2,
+.col-md-2,
+.col-lg-2,
+.col-xs-3,
+.col-sm-3,
+.col-md-3,
+.col-lg-3,
+.col-xs-4,
+.col-sm-4,
+.col-md-4,
+.col-lg-4,
+.col-xs-5,
+.col-sm-5,
+.col-md-5,
+.col-lg-5,
+.col-xs-6,
+.col-sm-6,
+.col-md-6,
+.col-lg-6,
+.col-xs-7,
+.col-sm-7,
+.col-md-7,
+.col-lg-7,
+.col-xs-8,
+.col-sm-8,
+.col-md-8,
+.col-lg-8,
+.col-xs-9,
+.col-sm-9,
+.col-md-9,
+.col-lg-9,
+.col-xs-10,
+.col-sm-10,
+.col-md-10,
+.col-lg-10,
+.col-xs-11,
+.col-sm-11,
+.col-md-11,
+.col-lg-11,
+.col-xs-12,
+.col-sm-12,
+.col-md-12,
+.col-lg-12 {
   position: relative;
   min-height: 1px;
   padding-left: 15px;
   padding-right: 15px;
 }
-.col-xs-1, .col-xs-2, .col-xs-3, .col-xs-4, .col-xs-5, .col-xs-6, .col-xs-7, .col-xs-8, .col-xs-9, .col-xs-10, .col-xs-11, .col-xs-12 {
+.col-xs-1,
+.col-xs-2,
+.col-xs-3,
+.col-xs-4,
+.col-xs-5,
+.col-xs-6,
+.col-xs-7,
+.col-xs-8,
+.col-xs-9,
+.col-xs-10,
+.col-xs-11,
+.col-xs-12 {
   float: left;
 }
 .col-xs-12 {
@@ -956,7 +1014,18 @@ pre code {
   margin-left: 0%;
 }
 @media (min-width: 768px) {
-  .col-sm-1, .col-sm-2, .col-sm-3, .col-sm-4, .col-sm-5, .col-sm-6, .col-sm-7, .col-sm-8, .col-sm-9, .col-sm-10, .col-sm-11, .col-sm-12 {
+  .col-sm-1,
+  .col-sm-2,
+  .col-sm-3,
+  .col-sm-4,
+  .col-sm-5,
+  .col-sm-6,
+  .col-sm-7,
+  .col-sm-8,
+  .col-sm-9,
+  .col-sm-10,
+  .col-sm-11,
+  .col-sm-12 {
     float: left;
   }
   .col-sm-12 {
@@ -1114,7 +1183,18 @@ pre code {
   }
 }
 @media (min-width: 992px) {
-  .col-md-1, .col-md-2, .col-md-3, .col-md-4, .col-md-5, .col-md-6, .col-md-7, .col-md-8, .col-md-9, .col-md-10, .col-md-11, .col-md-12 {
+  .col-md-1,
+  .col-md-2,
+  .col-md-3,
+  .col-md-4,
+  .col-md-5,
+  .col-md-6,
+  .col-md-7,
+  .col-md-8,
+  .col-md-9,
+  .col-md-10,
+  .col-md-11,
+  .col-md-12 {
     float: left;
   }
   .col-md-12 {
@@ -1272,7 +1352,18 @@ pre code {
   }
 }
 @media (min-width: 1200px) {
-  .col-lg-1, .col-lg-2, .col-lg-3, .col-lg-4, .col-lg-5, .col-lg-6, .col-lg-7, .col-lg-8, .col-lg-9, .col-lg-10, .col-lg-11, .col-lg-12 {
+  .col-lg-1,
+  .col-lg-2,
+  .col-lg-3,
+  .col-lg-4,
+  .col-lg-5,
+  .col-lg-6,
+  .col-lg-7,
+  .col-lg-8,
+  .col-lg-9,
+  .col-lg-10,
+  .col-lg-11,
+  .col-lg-12 {
     float: left;
   }
   .col-lg-12 {
@@ -3885,7 +3976,7 @@ fieldset[disabled] .navbar-inverse .btn-link:focus {
 }
 .label {
   display: inline;
-  padding: .2em .6em .3em;
+  padding: 0.2em 0.6em 0.3em;
   font-size: 75%;
   font-weight: bold;
   line-height: 1;
@@ -3893,7 +3984,7 @@ fieldset[disabled] .navbar-inverse .btn-link:focus {
   text-align: center;
   white-space: nowrap;
   vertical-align: baseline;
-  border-radius: .25em;
+  border-radius: 0.25em;
 }
 a.label:hover,
 a.label:focus {
@@ -4815,7 +4906,7 @@ button.close {
   position: absolute;
   z-index: 1070;
   display: block;
-  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
+  font-family: -apple-system, BlinkMacSystemFont, Helvetica, Arial, sans-serif;
   font-style: normal;
   font-weight: normal;
   letter-spacing: normal;
@@ -4933,7 +5024,7 @@ button.close {
   display: none;
   max-width: 276px;
   padding: 1px;
-  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
+  font-family: -apple-system, BlinkMacSystemFont, Helvetica, Arial, sans-serif;
   font-style: normal;
   font-weight: normal;
   letter-spacing: normal;

stuff/bootstrap/variables.less

@@ -42,7 +42,7 @@
 //
 //## Font, line-height, and color for body text, headings, and more.
 
-@font-family-sans-serif:  -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
+@font-family-sans-serif:  -apple-system, BlinkMacSystemFont, Helvetica, Arial, sans-serif;
 @font-family-serif:       Georgia, "Times New Roman", Times, serif;
 //** Default monospace fonts for `<code>`, `<kbd>`, and `<pre>`.
 @font-family-monospace:   "Lucida Console", Monaco, monospace;