In MobileFrontend the following css rules share the same rules and should be generalised/cleaned up (yes this is a micro-optimisation but a good opportunity to rethink/refactor):

{.mw-ui-button} AND {.notification-count} share 4 declarations

• border-radius: 2px
• display: inline-block
• font-weight: bold
• text-align: center

{.mw-ui-button.mw-ui-constructive}, {.mw-ui-button.mw-ui-destructive} AND {.mw-ui-button.mw-ui-progressive,.mw-ui-button.mw-ui-primary} share 4 declarations

• border-style: solid
• border-width: 1px
• color: #fff
• text-shadow: 0 1px rgba(0,0,0,0.1)

{.mw-ui-button} AND {.view-border-box *,.view-border-box} share 3 declarations

• -moz-box-sizing: border-box
• -webkit-box-sizing: border-box
• box-sizing: border-box

{.mw-ui-button} AND {.stable .pre-content .tagline,.heading-holder .tagline} share 3 declarations

• color: #555
• margin-left: 0
• margin-right: 0

{#page-actions li} AND {.mw-ui-button} share 3 declarations

• cursor: pointer
• display: inline-block
• margin-right: 0

{.cloaked-element} AND {blockquote:before} share 3 declarations

• left: 0
• position: absolute
• top: 0

{.cloaked-element} AND {blockquote:after} share 3 declarations

• bottom: 0
• position: absolute
• right: 0

{.content table.infobox th,.content table.infobox td} AND {.content table.wikitable > tr > th,.content table.wikitable > tr > td,.content table.wikitable > * > tr > th,.content table.wikitable > * > tr > td} share 3 declarations

• border-bottom-style: solid
• border-bottom-width: 1px
• padding: .2em

{.cloaked-element} AND {.mw-ui-icon.mw-ui-icon-element:before} share 3 declarations

• left: 0
• position: absolute
• right: 0