龍旂 is the dragon flag of Chinese emperors. https://kotobank.jp/word/%E7%AB%9C%E6%97%97-658618 A computer flag is フラグ (furagu). https://jisho.org/search/%E3%83%95%E3%83%A9%E3%82%B0
Going from フラグ to 龍旂 is no less weird than going from English "flag" to "dragon."
风 and 极 are Simplified Chinese. The corresponding Japanese characters are 風 and 極 and they don't connect to defaults or limits in software either. Now it's of course possible that 松本武 is not Matsumoto Takeshi (松本•武) but instead Song Benwu (松•本武) and the original message was in Chinese, but that doesn't explain the curious word choice either.
I don't speak Japanese so took a left field shot using Chinese - simplified characters used because that easier for me as non Chinese person to write. From everyday experience some really weird phrases are people recycling old expressions so I took a few minutes look for old Chinese words that might fit. And Japan still uses trad Chinese characters as one of its writing systems. So putting my small brain and some imagination, and 5 decades of messing with software, this was what I came up with. Purely my intellectual exercise shared in the hope of triggering someone with actual/better answer.
> simplified characters used because that easier for me as non Chinese person to write
Really? What makes one style or the other easier for you to write?
Note that you didn't actually succeed at using simplified characters; 风 is simplified, but 龍 isn't.
> And Japan still uses trad Chinese characters as one of its writing systems.
No, that's just false. They use their own system, which involves some characters that match traditional Chinese, some characters that match simplified Chinese, and some characters that are specific to Japanese.
It's usually best to share such caveats upfront, because people tend to be pretty trusting that statements that sound like they would require substantial expertise to produce are in fact produced by someone with such expertise. See also: people in this thread sharing whatever ChatGPT came up with, even though it's nonsense if you know how to tell the difference.