Leadership is indeed a tricky thing. As PC's gain respect in the world, they get certain benefits that seem to blur the line with the feat. This is, in my opinion, as it should be, and it's up to the DM to maintain the right balance. I think at times people expect too much from the rules and that they should explain everything in detail. This is an RPG and part of that is the unique human element that each DM brings to the game to make it interesting. Rules can never substitute for judgement or sense of story, and they can never develop a great campaign. They are the tools to build the house, not the blueprint.
So let's be more detailed for a minute. Each one of the PCs has an ability to exert influence on others. It is based on some mechanics (feats) and some personal charisma, and some level of contribution. This information is apparent to all of us in game, but not necessarily to the readership, since much of the "juice" is hidden from Kayleigh's point of view or from the action.
The group as a whole can call on the dragons for aid. They request, rather than order, but their request is likely to be granted based on all the valuable contributions they've made over time.
Scorch: Head of the guild, no feats involved. The guild operates almost purely out of self interest. Scorch would have to cajole cooperation from someone. His status gives him a chance to be heard, but the inducements he offered would more likely determine the answer.
Aethramyr: No leadership roles, no feats involved. Aethramyr is respected by the people of the Testing. He could ask them for aid, but not order it. He would certainly be given thorough consideration, since he has contributed to the cause of those people and on religuious grounds. But they would resist any request that would be too costly. Had he the feat, a likely game effect would be more of a willingness to ignore the cost of a request, and/or a better ability to order rather than ask.
Dravot: Leadership role, leadership feat. The perfect combination of story and mechanics supporting each other. His power and influence are both temporal and spiritual. Even the highest elders of the church would have to have a pretty damn good reason to refuse a request/order he made. It has nothing to do with hit dice or numbers of guys in armor - it represents the both the reach of his feat and the reach of his character in the world. It also represents the fact that humans are generally more inclined to obey authority in this context.
Bolo: Implied leadership role, no feats involved. Druids on the other hand are not easily led. Their very nature is contrary to it. Bolo, as a high ranking druid, could make requests, but the response would be driven by the need and his ability to make his case.
Valanthe: No leadership role, no feats involved. Perhaps the far end of the spectrum for this discussion. Valanthe is the least of a "people person". There are no religious orders, no monarchy, no guild that she influences. Such entanglements would be too constrictive for her anyway. The only organization she could tap on would be on the Shadow Plane. And while she has a reputation there, and she has contributed to their cause, she has no ability to order anything, and limited ability to request. Valanthe is not one to look elsewhere for aid in any case.
Kayleigh: Leadership role, no feats involved. Elves too are not easily commanded, but are more organized than the druids. Kayleigh has no troops per se, but if she was in the field and gave orders to an elven military unit, her orders would most likely be obeyed. The champions have no formal rank, but massive informal rank. Combined with her personal reputation and contributions to the elven people, she could get a lot of support if needed. But most of this comes from her personal qualities and experiences and elven culture rather than a feat. Had she the leadership feat, that might manifest in troops under direct command, or a champion cohort.
In each case, the character's base level of influence is more driven by what they've done (remember - actions have consequences

) than the feat. What the feat does is cover the degree of response and decrease the amount of justification needed.