My supervisor made comments like you’re too old for the job. Is that evidence of age discrimination?

Yes, it is evidence of age discrimination and could be enough to take a case to the jury. It may not be enough to establish a claim under the ADEA as some courts say that stray comments here and there do not suffice to establish a claim. But, that evidence could be smoking gun evidence in other cases. It certainly helps an age discrimination case to have this type of evidence.