why do you write Latin with all those diacritical marks? is this a British vs. American thing?
They mark long vowels. I don’t know how much you Latin, but for the benefit of anyone who doesn’t: in the archaic and classical pronunciations of Latin every vowel (except ‘y’, which was a Greek import) came in long and short varieties. Obviously you need to know the difference if you’re saying words out loud and it can sometimes also make a difference to the meaning of a word (e.g. ‘móra magna’ means ‘big blackberries’ but ‘mora magna’ means ‘a big delay’). It’s also important in understanding how lines of verse scan. Often the Romans didn’t mark the difference between long and short vowels in writing, but sometimes they did.
The first idea (supposedly suggested by the playwright Lúcius Accius in the second century BC) was that for a long vowel you just write the letter twice (e.g. Luucius), except for ‘i’ because ‘ii’ already occurs in Latin as a two-syllable sound so for that they either wrote ‘ei’ (which at that time sounded very similar to a long ‘i’) or just wrote the ‘i’ extra tall.
By the late republic that fell out of fashion a bit and the new idea was to write an ‘apex’ above the long vowel. The republican apex was shaped like an apostrophe or sometimes like a small number 7; imperial apicés were more like acute accents, though they tended to be a bit longer and steeper.
Modern classicists, when they want to mark long vowels, generally use macrons (e.g. Lūcius).
I try to mark long vowels whenever I can because it’s generally helpful but especially because I want Latin to be a language of conversation, not just a language for reading old texts. Even people who can read and write Latin very well are often shy about trying to speak it, and anything that makes that easier is a good thing, including anything that helps with pronunciation.
And I prefer apicés to macrons for three reasons. First, apicés are what the Romans used, so why reinvent the wheel? Second, macrons are also often used to mark ‘long’ or ‘heavy’ syllables for the purposes of verse scansion, which is a different thing, and a diacritic that could mean either of two things is maybe not terribly helpful to readers. Last, an apex is much easier to type on my keyboard (and most western keyboards) than a macron!