Good day!
Prehistory.

User has created a material in "category1."JoomSEF give link example.com/category1/material

users send comments to this material.

When website admin change category1 material to category2, joomsef publish web link example.com/category2/material

And here we have an interesting thing. All comments that were created before the admin changed the category have link:
example.com/category1/material#comment-3458

not visible, or rather JoomSEF throws a 404 page

When user add new comments after changing category, joomsef makes link correct:
example.com/category2/material#comment-3459

i try to clean cash and purge sef url - it doesn't help....

hey, anyone!

What handling do you use for the JComments component in JoomSEF? You can find out in JoomSEF -> Manage Extensions -> JComments -> Common tab.
What does the comment URL look like if you disable SEF completely in your Joomla's global configuration?

joomsef for jcomments is disabled

In that case the link is generated by Joomla itself, which means that JComments itself is probably creating wrong URLs for renamed categories.
Or maybe the old URLs are just cached, so try clearing the cache in Joomla.

cashe in joomla was cleaned....
it doesn't help ;(