Until this gets officially fixed, here’s a CSS style you can use with extensions like Stylish for Chrome:
.Node.is-checked .Node > .Node-self > .Node-checkbox:after {
opacity: 0;
}
.Node.is-checked > .Node-self > .Node-checkbox:after {
opacity: 1 !important;
}
.Node.is-checked .Node > .Node-self > .Node-contentContainer > .Node-content,
.Node.is-checked .Node > .Node-self > .Node-contentContainer > .Node-renderedContent {
text-decoration: inherit;
}
.Node.is-checked > .Node-self > .Node-contentContainer > .Node-content,
.Node.is-checked > .Node-self > .Node-contentContainer > .Node-renderedContent {
text-decoration: line-through !important;
}