Thanks for a very full and courteous reply. I see now where you are coming from - and, now that I know, I have set my own default to 300px, which better suits my ageing eyes. I am still a little puzzled, though. As was pointed out in the debate at Image_use_policy/Archive_8#Forced_image_size, if the image size for a thumb is not specified, it forces the default image size (currently 180px) on any user who is using Wikipedia solely for reference and does not have an account. Whose preference does this reflect? For many images, 180px is simply too small for the image to achieve its illustrative purpose; moreover, this possibility is explicitly recognised in the full text of the recommendation you quote above (unless ... a size is specified outside the range of widths 120–300px that can be set in the preferences). 

 Also, a recommendation is, by definition, not a policy. Surely, then, it is not appropriate to "enforce" it retrospectively on other editors' work? 

 You will see that I have now read up the debate on this issue. So far, I have yet to read anything to convince me that my views are unreasonable; however, I am still open to persuasion. Thanks for your time & patience. Regards,