I am not a fan of tagging pages with {{refimprove}} as opposed to using {{citation needed}} tags, unless the page has very obvious and extensive issues with references (or BLPs). Refimprove tags are, in my opinion, quite ugly and unsightly things. They also make the page content start later and take up much space. Citation needed tags on the other hand do not take much space and are also more specific.
Although the requirement of minimal change in direct quotations is strict, a few purely typographical elements of quoted text should be conformed to English Wikipedia's conventions without comment. These include the following:
Use the style chosen for the article: unspaced em dash or spaced en dash.
Set apostrophes and quotation marks straight, not curly.
Remove spaces before punctuation such as periods, colons, and %.
When integrating the quotation into the grammar of a larger sentence, downcase the first letter of a quotation that is in upper case purely because it starts a sentence in the source (It turned out to be true that "a penny saved is a penny earned").
But generally preserve bold and italic face, and the variety of English.
