I posted this question on another website but did not receive any answer.
The thing is that I have a lot of different versions of the Greek New Testament, and they all seem to follow more or less unique rules when it comes to their use of punctuation marks. For example, the Byzantine NT always writes a capital letter after dots and Greek question marks; this is not the case in the NA28 or Scrivener NT. The Byzantine NT and Scrivener NT also very often place a comma before “και” and kind of mimic the way it is used in modern English. The Scrivener NT also uses parantheses, while the rest of the texts instead use commas.
Are there any standard rules for which punctuation marks should be used in ancient Greek texts, and how?
Editorial practice varies but only slightly and there’s no universally accepted model to follow, though it’s conventional to insert spaces between words as in written modern languages. Ancient Greek manuscripts made no distinction between upper and lower case, and punctuation varied enormously. The Greek question mark (“;”) was a medieval invention and there’s no good reason to use it. My own preference in fact would be for wholesale adoption of modern punctuation (“?” and “!” included), but there’s little chance of that in such a hidebound field. Best practice is to reserve upper case for the initial letter of proper names (and not for the first letter of sentences) and in general to punctuate as e.g. Oxford Classical Texts do—or however you like.