"even more understandable" is grammatically correct and can be used in written English.
It is used to emphasize that something is already understandable, but can still be made even more understandable. Example: "The teacher's explanation made the concept even more understandable for the students."
If anything, yearning for a Philip Marlowe fix is even more understandable.
He insists his arm is sound, which makes it even more understandable to wonder if he is through.
If Russia wanted to attack Chechenya, it was no concern of ours, and then after 9/11, the idea of attacking perceived Islamic terrorists was even more understandable.
In that sense, the rage and dismay all over social media are even more understandable: people up against distant conglomerates inevitably feel like mere specks shouting at monoliths.
The current popularity of flamenco may make it even more understandable if theatergoers think of Spanish dance primarily in terms of solos.
In the exciting main event, a bruising and undefeated welterweight named Keith Thurman battered Robert Guerrero, who had only lost twice before (once early in his career, which is understandable, and once to Mayweather, which is even more understandable).
Even more intuitively understandable appears to be a probabilistic statement.
Mr. Bloom's response, quoted in a 1996 catalog essay by the art historian Dorothy Abbott Thompson, was that he wanted to make the meaning of death "more understandable, even more acceptable, more familiar, more knowable".
In some ways DJ Hero 2 is even more accessible and immediately understandable than rock 'n' roll games like Rock Band and Guitar Hero.
To use his position in an effort to influence public officials to alter the content and implementation of the Constitution is even more disturbing and less understandable.
Let's separate this up, even more to make it understandable to even the most clueless of people.
