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The common usage of something like philosopher or historian or anthropologist generally assumes you're educated to a master's/PhD level, and study the topic as your "profession".

but to your point, a philosopher can be anyone who takes the topic seriously and devotes time to it. They might be categorized as amateurs or enthusiasts, but there are certainly people within those categories who make significant advancements to their fields.

It only really matters when some sort of professional designation or licensing or legal standing comes up.

It doesn't matter what goofballs on the internet say. If someone's got good ideas, they'll bubble up.