More than half of the tags that only had one instance were removed or retagged.
In the process, some collapsing of duplicates (network, networks, networking / video, videos, movie, movies)
Then, all of the tags with zero entries were removed.
THEN! With LJ-SEC, I tagged all untagged messages with "untagged"
Now, it's not cleaned up like I want it to be, but the immediate problem of having exhausted the maximum number of tags per journal was alleviated by far. (Down to roughly 575 from 1000)