It may be true that "Most pages do not have custom HTML", but that is largely because: 1) a great many listings have only rudimentary (near skeletal) descriptions, and 2) a great many contributors had no knowledge of HTML, and/or no interest in spending any time dressing up their listings by using anything more than simple text. But a handful of the most avid volunteers (many of whom maintain(ed) web pages of their own) have used HTML to add quality to many of their listings. I (and I'm sure many others) enjoyed seeing these spiffy additions, and wished there were more HTML-aware people caretaking more listings.
That said, pages with 'custom HTML' are not the ones impacted! It took no custom HTML to create 'data blocks': two or more consecutive short lines of related information (with no blank lines between them), followed by a blank line before the next data block or regular paragraph of description. With this latest change, the lines of data within each block now have blank lines inserted between them, stringing them out down the page, undoing the 'data block' appearance.
The characterization that it will take merely "a few seconds of formatting" to fix each of these pages is flippant. It takes a few seconds to pull up each listing, a few more seconds to scroll through the description to check for formatting mangled by the change, then about a minute for the simplest of fixes (and more for multiple or more complex fixes) to carefully reformat things to look decent again, then a few seconds to save and type a 'change comment'. (For the 'data blocks' I cited above, it seems to require switching to "Preformatted" to delete the unwanted newly inserted blank lines, then back to "Paragraph" to return any other formatting as it was before. I have no idea what time and work-arounds it may take to remedy more complex custom HTML!)
For the gauge changes back in November there was a list of affected listings (I.E., river/reach), which automatically removed a listing from the list when it had been fixed. With no such list possible/available this time, this change (if we really want to be thorough) requires going into EVERY listing in EVERY state, to find which ones have been adversely affected. Then making the change, saving the change, and (however we do so on our own) keeping track of which listings we've looked at (and fixed, when needed) to know which ones remain to be looked at.
If removing all custom HTML was the only way for the river pages to work across all platforms, then perhaps it was a necessary move. However, as with a few times before, these cited remarks again show a casual disregard for the impact and serious demand of time these changes make on the most dedicated, conscientious, and long-serving volunteers.