By far the most prevalent use I see is Wiktionary's #3 'one who gatekeeps' > verb #5:

> (by extension, slang, Internet) To limit another party's participation in a collective identity or activity, usually due to undue pettiness, resentment, or overprotectiveness.

But in the (today) rarer, less metaphorical sense... It's not that either? What is Twitter guarding access to? It's not, we're talking about Twitter itself.

My view is that "gatekeeper" used to - and still does - mean someone or something with actual power over belonging to something, and by extension "gatekeeping" commonly means someone who doesn't have actual power but tries to exert social influence as if they decided who does and doesn't participate in or belong to a thing. I think the two meanings continue to coexist depending on context.

> My view is that "gatekeeper" used to - and still does - mean someone or something with actual power over belonging to something, and by extension "gatekeeping" commonly means someone who doesn't have actual power but tries to exert social influence as if they decided who does and doesn't participate in or belong to a thing.

From a straight up grammatical perspective, I'm not sure what you're saying makes sense, or really what you're trying to say. What you're saying "gatekeeper" means tracks just fine. But I'm getting thrown for a loop with "gatekeeping" because that's either a verb (e.g. "The dog is gatekeeping.") or an adjective (e.g. "The gatekeeping dog..."), but you're giving it a meaning that only works for a noun ("someone who doesn't have actual power but..."). Basically, I don't understand what you're trying to say, but what you're saying seems like something I'd like to understand.

As far as grammar goes, I think I was implying that "gatekeeper" does suggest the older meaning more, and "gatekeeping" the newer meaning. But I'm not sure if that's a rigid rule or why the pattern exists.