As long as the edit improves the post, I'd say the edit should be approved. The system already has a check in place that enforces that the user does not change "just one comma" or a similar low amount of characters.
„Als man sich gerade über die Beschießung von Shanghai durch die Japaner erregte und ich Karl Kraus bei einem der berühmten Beistrich-Probleme antraf, sagte er ungefähr: Ich weiß, daß das alles sinnlos ist, wenn das Haus in Brand steht. Aber solange das irgend möglich ist, muß ich das machen, denn hätten die Leute, die dazu verpflichtet sind, immer darauf geachtet, daß die Beistriche am richtigen Platz stehen, so würde Shanghai nicht brennen.“
Wikipedia: Karl Kraus
Even if the source view for the edited post apparently has just empty spaces added this might lead to a significant improvement in readability and legibility, a greater attractiveness of the rendered output.
That said, insubstantial edits usually clog up the review queues and that is a known problem on smallish beta-sites. This gets worse if one user in particular finds this supposedly "safe & easy rep-gainer method" and suggests a whole bunch of small edits.
This problem might be fixed to a degree by somehow contacting the low-rep but industrious editor and reminding him in some wy or form (in a comment, by pinging him in chat) that once he opens the edit window he should really strive the hardest and with the most diligence to really fix all and everything he sees in need of fixing and improvement.
I think the last paragraph is the most important part to get right. And my suggestion might not be the right way. It might be seen as abusing the comment system? So, further improvements for this post are needed as well. This time on the content level as well.
You are invited to edit!