A few years ago, Yandex introduced a new algorithm for the Russian search engine market that instructed webmasters to use no more than 20% of the text in their content to be captions and tags.
The rest of the text was available for a user’s searches, but it was very obvious when you did that kind of search if something that would be relevant to your query had been used as an answer. This was a main reason why Yandex changed their algorithm.
In addition, in 2017 Yandex introduced another algorithmic update that made no distinction between words and non-words (i.e., keywords).
That meant that adding a single character (e.g., the letter “i”) to the beginning of a word, making it a keyword, did not change its probability of appearing in a search query or its ranking.
This is why the practice of keyword stuffing is considered to be an infringement of Yandex’s rules for site owners.
According to the terms and conditions for the Russian search engine market, there are specific guidelines that webmasters must adhere to when they create web pages.
One of these is that you should not deny access to your content by way of keywords at all. To achieve this, you should only use 9 to 10% of your text as keywords – this was already determined by Yandex at an earlier date.