I only ran things for tags used 10 or more times, and a diary qualifies if any of its tags pass that threshold.

For several months, I've been cleaning tags for an hour - sometimes more - a day. Sometimes quite a bit more: it's quite habit forming. Mostly, I've been correcting spelling errors, adding first names and eliminating singleton and duplicate tags. When there was a clear favorite, I've consolidated tags in cases where two or more were used to refer to the same thing... and got into a little trouble when I took on versions of Walter Reed Army Medical Center... which is now "Walter Reed" and "Army Medical Center."

I mention all this because it leads to eliminating tags that are used fewer than 30 times. Which, if I understand you, should increase the numbers of diaries with tags that pass the threshold.

I've noticed cluster of tags - it speeds up the clean-up - and am interested in what you'll write about clusters.

Side by side columns would be handy.