Some (opinionated) style tweaks, for a nicer Mastodon web interface. Use with the Stylus browser extension, or with the user style tool of your preference. These styles do not make any assumptions about color scheme. I built them for my own use, on Firefox on a Mac desktop. Untested on other browsers, no warranty, free to use and modify.

masto-userstyles.css

/* Modified desktop layout for Mastodon, Hometown, etc. */

/* creator: @nicepersonality@mspsocial.net */
/* last modified: 2022-12-01 */

/* Fonts and font size */
.ui {
  font-family: 'Libre Franklin', system-ui, sans-serif;
  /* I haven’t had much success in @importing web fonts within Stylus, */
  /* so I use a font I have installed locally. Feel free to substitute */
  font-size: 1rem;
  line-height: 1.375rem;
}
.status__info {
  font-size: 1rem;
  line-height: 1.375rem;
}
.status__content {
  font-size: 1rem;
  line-height: 1.375rem;
}

/* Neater columns that adjust to window width */
.columns-area .drawer,
.columns-area .column {
  min-width: 100vw;
  width: max(100%, 320px);
}

@media screen and (min-width: 640px) {
  .columns-area .drawer,
  .columns-area .column {
    min-width: 320px;
    width: 50%;
  }
}
@media screen and (min-width: 960px) {
  .columns-area .drawer,
  .columns-area .column {
    width: 33.333%;
  }
}
@media screen and (min-width: 1280px) {
  .columns-area .drawer,
  .columns-area .column {
    width: 25%;
  }
}
@media screen and (min-width: 1600px) {
  .columns-area .drawer,
  .columns-area .column {
    width: 20%;
  }
}

/* Status layout adjustments */

/* Full-width status text */
.status,
.detailed-status {
  margin: 0 0 0.5rem;
  padding: 0.5rem 0;
}
.status > *,
.detailed-status > * {
  margin-left: 1rem;
  margin-right: 1.5rem;
}

/* Full-width boost & notification info */
.status__prepend,
.notification__message {
  margin: 0;
  padding: 0.5rem 0 0 1rem;
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: flex-start;
}
.status__prepend > *,
.notification__message > * {
  position: static;
  margin: 0;
  padding-right: 8px;
}

/* Larger avatars and stacked time & account info */
.status__relative-time {
  display: block;
  float: none;
  margin: 0;
  padding: 0;
}
.status__visibility-icon {
  padding-left: 0;
}
.status__info {
  position: relative;
  min-height: 72px;
  padding-left: 72px;
  line-height: 20px;
}
.status__avatar {
  top: 0;
  left: 2px;
  height: 60px;
  width: 60px;
}
.account__avatar {
  width: 60px !important;
  height: 60px !important;
  background-size: cover !important;
}
.account__avatar-overlay-base {
  width: 48px;
  height: 48px;
  background-size: cover;
}
.status__info .status__display-name {
  padding: 0;
}
.display-name__account {
  display: block;
  overflow-x: hidden;
  text-overflow: ellipsis;
}

/* Optional adjustments*/

/* Bigger in-message emoji now maintain consistent line heights */
.reply-indicator__content .emojione,
.status__content .emojione {
  height: 1em;
  width: 1em;
  vertical-align: text-bottom;
  transform: scale(1.4);
  margin: 0 0.2em;
}

/* Full-bleed visual media */
.status > .media-gallery,
.status > .video-player,
.detailed-status > .media-gallery,
.detailed-status > .video-player {
  margin: 0.5rem 0;
}
.media-gallery,
.media-gallery__item,
.video-player {
  border-radius: 0;
}

/* Less-obtrusive gallery overlay buttons */
.media-gallery button {
  opacity: 0;
  transition: opacity 0.3s ease-in-out;
}
.media-gallery:hover button,
.media-gallery:focus button,
.media-gallery:focus-within button {
  opacity: 1;
}