Note that YouTube censor bad words by replacing them with [__], so you can retrieve them by using [__].
As the website support regular expressions, you can exclude some channels by using ^((?!channelIdToExclude).)*$.
For instance find the presence of a YouTube channel on another one you can fill fields as follows:
channelIdToExclude
^((?!channelIdToExclude).)*$
You may be interested to use the following query format to look only for comments.
You can use the following query to search for the comments of a given channel: "value": "channelIdCommenting".
Note that if you want to share a comment to someone you can share the URL https://www.youtube.com/watch?v=VIDEO_ID&lc=COMMENT_ID and the comment will be the first one in the list. The same note applies for community post comments with the URL https://www.youtube.com/channel/UCgvqvBoSHB1ctlyyhoHrGwQ/community?lc=COMMENT_ID&lb=POST_ID. This also works for answers to comments.
Note that prepending (?i) to your regex makes it case insensitive.
Note that if you provide a channel id as a file path filter, the search will be far quicker by only proceeding to the search on the given channel.