It could be that my thread looks like a phishing scam because it contains a link, but all can see the link to YouTube and a moderator could test that for before deleting it and in my case it will always be 100% legit.
No good moderator/dev/admin will blindly follow a link (even for testing) as it could post a security risk to their own account. Most IT professionals would test links in a sandbox environment with a dummy account, but that will be too much hassle/time-consuming for the mods so they will just remove the post.

I think bottom line is your post had all the appearance of RMT/Phishing and it got shut down as a result (thought he forum rules do mention that advertising is prohibited, I think this is dealt with at mod discretion as they haven't removed your other posts). As others have noted, the forums are not the best place to reach out to the community in this way - if you want to run a giveaway, do it on a live Twitch stream - any other method is going to seem suspicious to most players. (Though doing a gil giveaway just to get more followers/likes is not a great way to do things anyway - you get followers/subscribers by creating useful and engaging content - look at the biggest FFXIV content creators out there, they didn't get where they are by trading gil for some likes/comments/follows).

I'd be surprised if they restored your post and to be honest, if you start creating similar ones they may even suspend your account (fair warning).