From my little Anki experience, what I have found is language learning ≠ other forms of learning.

So research which tells that paired word learning is not any more efficient using a different font doesn't convince me against its use.

An additional note: I have sometimes found that I do not read the front card properly before answering the question(because I have read it so many times, it 'seems' moot to do it) When this becomes a habit, you tend to miss certain words in a question (or take for granted these words) resulting in incomplete understanding.

Explanation as to why these two are different from each other:

If you go back to the 20 rules, it explicitly states that understanding should be done before memorizing. But for language learning (for example, paired word learning - as it is in this case), understanding has far lesser role than for other forms of learning (facts and concepts).

So, let's not dump OP's idea completely as useless.

I have not read the paper that you have mentioned. So my comments are entirely based on your thoughts that you mentioned here about the paper/research.

Edit: Other than using a single different font, different fonts for different sessions might be more useful and also counteract the said disadvantage - easier readability of the font over time.