1. I am concerned about the sorting of the suggestions using both the quality and count properties. Which one should take precedence?

There's nothing in the code to suggest that the suggestions with quality of 1 will always appear at the top of the list of suggestions.

Change 770448 had a related patch set uploaded (by Wangombe; author: Wangombe):

[mediawiki/extensions/Translate@master] Sort suggestions with same percentage by usage

https://gerrit.wikimedia.org/r/770448

Here's my recommendation:

1. Sort on the basis of similarity / matching % (100%)
2. Then sort on the basis of the number of uses

Currently the order is done on the backend. See: https://gerrit.wikimedia.org/g/mediawiki/extensions/Translate/+/54c5b26dd7a8dc1d02ccd98081ebe02cf3b61239/ttmserver/ElasticSearchTTMServer.php#224

I recommend doing the sorting on the basis of usage there itself if possible.

Sorting with Eugene's latest patch and test data:

Change 770448 merged by jenkins-bot:

[mediawiki/extensions/Translate@master] Translation Memory: Sort suggestions with same percentage by usage

https://gerrit.wikimedia.org/r/770448