Accent is not just the actual tones and sound of actual speech but also the sentence construction, word selection and style that influence the voice heard in a reader's mind.

As an example looking at your second sentence.

"Honest question, where did you FIND his accent in the text". It might have been better phrased as "where did you hear/read/see/detect the accent in his text?" Find isn't quite the right choice to my eye.

This was a minor error that could have been a simple typo but is also a typical error of a non-native english speaker. If you made mistakes like this repeatedly over a longer post it would influence the voice we heard as we read your post.

This is not a huge issue or something you should worry about beyond just noticing and self improving over time.

(I would not have particularly noticed or disapproved of your sentence if you hadn't asked.)

The blog post was missing several words in the first few paragraphs and had some awkward constructions. It was largely ok reading for a technical post but there was definitely an "accent" that emerged from reading it.

You have the correct interpretation of the English word "accent." An accent pertains to spoken language (e.g., pronunciation and prosody). It is only in a loose or figurative manner of speaking that you could talk about the accent of a text.

If you're reading text written by an individual, it is certainly possible for the text to be written with an accent and/or interpreted with one. Maybe the mind tends to do this more when it knows the person or where they are from -- I do not know.

As a native English speaker who has spent a number of years learning Russian, I can only offer my interpretation of what parent meant. Most of the "accent" might be coming from the incorrect use of articles. The Russian language does not use articles like English does, and my teacher (among others) say this is the hardest part of English for native Russian speakers to learn because it is so foreign (much like an English speaker learning to decline every word in a Russian sentence). I live in NYC and spent a lot of time around English speaking Russians and once you hear what I'm referring to, you can't un-hear it.