I'm not sure any of the vegans I know would give up veganism in order to minimize their scars any more than the meat-eaters I know would give up meat based on studies that show it can be mildly unhealthy.
Very large effects are unlikely given the number of long-term vegans who seem to maintain sufficient health. Whereas small effects might be considered a worthwhile sacrifice.
[To clarify: I am not qualified to judge the general healthiness of any particular diet -- any sufficiently popular diet seems to have conflicting studies showing it is "healthy" and others showing it is "unhealthy". The point I intended to make above was that most people either outright reject or remain unswayed by these kinds of studies.]