Despite promise, theme tags changed, messing up custom CSS

In post https://help.zoho.com/portal/en/community/topic/zoho-wiki-custom-css-scope-and-base-theme on Oct 1, I asked which theme I should adopt as a base for applying custom CSS.

Reply from Revathi Priya said: "We assure you that the page structure, tags will not be changed and that will not affect your Custom CSS ." and gave an example of Cornflower Ribbon.

So I did a lot of work based on Cornflower Ribbon. And today, three weeks later, I see that the html has changed, messing up some elements to which we had applied CSS!

Specifically, the following elements:

[div id="pageButtonId"]
[div id="editlink" class="pageButtonShow"] Edit button
[div class="pageButtonShow" id="zwMorePageOptions"] Page options button

changed to

[ul id="pageButtonId"]
[li class="pageButtonShow zw-editbtn" id="editlink"] Edit button
[li class="pageButtonShow zw-morebtn" title="Page options" id="zwMorePageOptions"] Page options button

Aside from the annoyance of this breaking the work we had done, it raises the larger question --

How to we proceed to have a stable site that doesn't require frequent admin/developer attention to fix broken CSS? Should we migrate to a different theme? Is there some arrangement we can make to NOT update to successive html revisions?

Thanks,

- Graham

My issue tracking Id: GWZ1023