The keyword term "patriot day reddit" is a noun phrase. The main point of the phrase, and its grammatical head, is the proper noun "Reddit." The preceding term, "Patriot Day," which is also a proper noun, functions as a modifier.
In this construction, "Patriot Day" acts as a noun adjunct or an attributive noun. A noun adjunct is a noun that modifies another noun and functions like an adjective. It specifies the nature, topic, or type of the head noun. In this case, "Patriot Day" specifies the subject matter of the content or community being sought on the platform identified by the noun "Reddit."
For the purpose of an article, this grammatical analysis indicates that the primary subject is the Reddit platform itself, specifically in the context of discussions, communities (subreddits), or content related to Patriot Day. The core part of speech to focus on as the main subject is the noun "Reddit," as qualified by the topic "Patriot Day."