Well, I can see my post hasn't been published or disappeared.
It's good to do these changes on your localhost, not on your live site.
Well, it works only on simple templates like 'Article' or 'Mini article', without any additional fields.
OK, here's my shortened solution.
1. Go to PhpMyAdmin, and export 'xxx_content' table with REPLACE option.
2. Find a query to be replaced. In my Seblod it was:
::jseblod::article::/jseblod::
::panel_article:: ::/panel_article::
::wysiwyg_introtext::
and
::/wysiwyg_introtext::
::wysiwyg_fulltext:: ::/wysiwyg_fulltext::
::panel_article_details:: ::/panel_article_details::
::panel_article_params:: ::/panel_article_params::
::panel_article_meta:: ::/panel_article_meta::
::panel_end:: ::/panel_end::
::jseblodend::::/jseblodend::
3. Open your SQL file with an advanced editor i.e. Notepad2.
4. Copy the unwanted markup, choose Replace (Ctrl-H) function, paste into a first textbox.
In a second one don't write anything. Run the command Replace.
5. Repeat 4th point with another markup (if applicable).
6. Save SQL file with different name.
7. Open PhpMyAdmin again, import changed table.
8. Go into Joomla Admin, refresh your cache.
9. Open your site. Markup shouldn't be seen anymore.