I believe that what Benthamite was trying to get at was the fact that this post isn't an ad for 80,000 Hours itself- it provides very little to no information about 80,000 Hours itself, what 80,000 hours does, who is involved in it, etc- the sort of information one would find in an actual ad for the organization.

Instead, it advertises a specific service. However, even here the word "advertise" is sneaking in negative connotations, particularly in this context- advertising has connotations of conniving Madison Avenue executives thinking of sneaky and/or pushy ways to take your money, whereas in this case 80,000 Hours is offering a free service. (Incidentally, advertising is so strongly associated with commercial products that it might be literally false that this is advertising, depending on which definition you use- for example, Google defines advertising as "The activity or profession of producing advertisements for commercial products or services;" this isn't a commercial product or service, so it's not advertising by that definition.)