The only difference here is that for the members in question we know for sure what their preferred pronouns are after interacting with them for years. Now that we know that you use masculine pronouns, everyone will make sure to apply them as we do for the others.To be fair, some other users (Merio, Steph, Ari) got their proper pronouns. The name Marcos (the Spanish form for Mark) is an unambiguously male name, so I fail to understand why I can't get the same respect and consideration as other users.
Also, you might have based your username on this male Spanish name, but it's the internet. For all we know, it could have come from a made-up country name for a roleplay you did a decade ago. Better to not assume in this case, I've seen the most cis hetero men use feminine profile pics and usernames. And while one could argue using they is assuming, it is almost widely accepted as the de facto pronoun when gender is unknown.
And not to forget that English is a very neutral language when it comes to gender and we have so few hints to base our conclusions on.
Take it from someone who has been addressed as he by half of this forum at least once.