(continued from above...)
Sometimes you use "points" (eg Chase points) that are treated as cash to pay for a flight on ANY airline. (This is the case where you get a 1.5X or 1.25X conversion rate referenced above.) In that case, you are effectively paying with cash, not points. The airline never sees anything about your points, they see you paid cash for the ticket. If anything goes wrong, you have the exact same rights and options, and are treated 100% the same, as every other happy passenger. The fact that you converted "points" to cash and then used that cash to pay for the ticket is not relevant (nor even visible) to the airline.
Sometimes tickets are paid for using the points in an airline's loyalty program (eg: you used United miles to book a flight on United or one of its partner airlines on United's website; or you used Delta miles to book a flight on Delta or one of its partners, on Delta's website). That's paying with points directly -- even if you transfer points to miles (you can do that with several bank "portals"), what counts is what currency was used for "payment" (actually, in the eyes of the airline, it's a "redemption" not a payment).
If you pay for your flight using miles/points which are converted to money (this is the case suggested above, for redeeming for a higher rate), then you are buying a ticket with money, and it's treated exactly the same as if you handed a pile of cash to a travel agent -- that is, if your flight is cancelled/delayed/nerfed, you are treated exactly the same as any other ticket holder. If you have a problem, you deal with the airline (whatever airline that is), NOT the "portal" people, and you have exactly the same rights, conveniences, etc.
If you pay for your flight with airline frequent flyer points (eg, on United's web site, paying with United's MileagePlus miles, or on Delta's website, paying with that airline's own currency), you still deal only with the airline (not some bank), but you MAY have fewer options in case you need to rebook -- it depends on the system you've bought into (and other variables, eg how bad is the meltdown, how helpful will the airline be). For most frequent flyer programs, if you travel on an "award ticket" (paid in miles), and you have to book a different flight, you may be limited in what flights are offered (same as when you originally booked). A few programs treat their "points" as cash equivalents (so you need to know the program's rules), in which case you have access to the same seats as anyone else. From a practical standpoint, when flights get cancelled, any airline will do what they can to get you to where they promised to get you, it just may take a while. I've got one itinerary in September booked with miles that has been changed 4 or 5 times due to a cancellation; they just keep rebooking me. If you book an award flight in business or first class, you may have limited options for the equivalent class of service in case of rebooking, but they will get you there eventually (if you insist on that lay-flat bed and the caviar, you may have to wait a while for an available seat).
How will you be treated by staff if things go south? How you paid for your ticket should not make any difference. In all cases the airline should help you without regard to how you paid for your ticket (because you bought it from that airline). Honestly, with the major melt-downs we are seeing, I think everyone is treated more or less the same -- the staff have limited options and they just do their best for everyone.
Bottom line is: the details matter. Be sure that you understand what you are (and what you are not) buying. A ticket bought through a "portal" may be just fine (depends on those details).
Hope this helps someone.