Here's a rough workaround in the form of a uBlock Origin filter, if this example benefits anyone:

    # bigger arrows; wider gap between arrows
    news.ycombinator.com##:xpath(//div[contains(@class,"votearrow")]):style(width: 15px !important; height: 15px !important; background-size: 15px !important; margin-bottom: 10px !important)

    # larger comment toolbar
    news.ycombinator.com##:xpath(//span[@class="comhead"]):style(font-size: 200% !important)

edit: And here's some examples of other peoples' HN filters:

https://hn.algolia.com/?query=%23%23%20ycombinator.com&type=...