Forename Capitalisation ~ Karl Drinkwater

Which is correct?

K.D. Wordman?
K. D. Wordman?
KD Wordman?

It's a tricky one. Basically, style guides differ on this. Especially because, technically, all the variants are correct.

According to Hart’s Rules (chapter six: Names) it would be K. D. Wordman with a space. BUT! They admit spaces and points are not always used, and they also make a mistake: they use J. K. Rowling as an example, when it is really J.K. Rowling with no space (see her Website/Twitter - it's something Wikipedia gets wrong too).

Incorrect, Wikipedia

According to newspaper styles such as Guardian Style (p160) it would be KD Wordman. Personally, I think that looks weird outside of newspapers.

For an author choosing how they wish to appear, and using multiple initials for their forenames, my general advice is to either pick a style guide and stick to it for consistency; or look at what other authors who write in your genre do, especially well-known ones. Hence using J.K. Rowling as an example.