The answer to this may be different to what you expect since in many countries (including the US, but not all countries!) a font is protected like a piece of software, and the design of the letters in the font are not protected at all. A copy is therefore defined by taking all or part of the original font file and actually copying it, possibly translating it to a different format or modifying it. If you are not doing this, it isn't a copy. In fact, if you were reproducing the same exact design of a typeface without actually touching/reading the original font file (or any representation of it in digital format, such as the file being converted to a different format), this would be fine (in such a country).
This is essentially a legal question, so it has a few problems being asked here - firstly it's not a community of legal professionals, and also laws vary by country. Copyright, however, is largely equivalent in most countries (though not necessarily for typefaces/fonts). I am not a legal professional.
Now if you are in a country where the design of the typeface can be protected by copyright, then you're essentially asking whether a typeface is protected from other people creating similar designs, even by chance.
While patents are like this, copyright is not. If you are not materially, mechanically or systematically (systematically might include techniques such as the grid method, or memorising and copying exact details one by one) copying someone else's work and any resemblance is purely an accident, it's not copying as defined by copyright. Even if you are "inspired" by a work and you set out to create a work in the same style, that alone still would not make it a "copy" as defined by copyright unless there was some substantial similarity not only in the style but there was evidence the design/wording itself was systematically copied or translated.
Of course, all this said, as unlikely as this is, if you did happen to design pretty much the exact same thing as someone else purely by chance, it may be impossible for a judge to determine whether it was a very statistically unlikely chance event or if you actually copied. Thankfully, in something as varied as a font or most non-trivial artworks, this is astronomically unlikely to happen if you didn't actually copy anything.