No such limit but it is always good to have 100+ completes so you can see good %ages across topics.

Alea as PeeyushBansal mentioned a higher number of responses will enhance precision. For the first pass, Qualtrics advises checking at least 15 to 20 verbatim responses per topic to get a good level of precision. The link below is a definitive guide to understand how Text iQ works https://www.qualtrics.com/experience-management/research/text-analysis/

Cheers
Abhi

According to this article, it will recommend topics once you have 500 comments, but there are not limits to how many you need in order to make your own topics from scratch or to upload their pre-existing topic packages. https://www.qualtrics.com/support/survey-platform/data-and-analysis-module/text-iq/topics-in-text-iq/#RecommendedTopics