Listing "memberships" on academic CV

The general rule is "if you don't want someone to ask you about it, don't put in on your CV." Including such memberships is still standard practice for many as they signify both your involvement and willingness to continue to participate in your field. So, don't think of these memberships as padding, think of them as opportunities to highlight your accomplishments - unless you really can't find a positive way to discuss these memberships, in which case they should not be included.

Many (but not most) people list membership in disciplinary organizations on their CV. If the membership is open to anyone who pays a fee, I consider listing this completely pointless. If membership is selective, then it is productive to list it. If somebody lists membership in a predatory or pseudoscientific organization on their CV, then I would view that as a negative.