Test case :
Linux 2.6.18-194.32.1.el5 x86_64 (CentOS5, python2.4 installed but not used to run Trac)
Python-2.7.1 (built with --enable-shared)
Trac-0.12.2-py2.7 (installed by easy_install-2.7, brought up by mod_wsgi)
add TracWysiwyg-0.12.0.3_r9676-py2.7 (installed by easy_install-2.7)
enable TracWysiwyg in Admin/Plugins panel
reload a ticket page and see Wysiwyg works in its editor fields
add TracTicketDelete-2.0.1-py2.7 (by easy_install-2.7)
enable TracTicketDelete in Admin/Plugins
reload a ticket page and see Wysiwyg does not work at all
disable TracTicketDelete, reload ticket, see Wysiwyg works again
Also I noticed that enabling TracTicketDelete breaks date chooser of 'TracDateField-1.0.1-py2.7' plugin
another case :
enable its 4 submodules listed in TimingAndEstimationPlugin#Components
reload ticket, see Wysiwyg works
enable the rest of timingandestimationplugin submodules,
reload ticket, see Wysiwyg breaks (Wysiwyg radio button is there, but on selecting it, edited text disappears, and reappears only on selecting Textarea radio-button again)
I narrowed this down to T&E submodules 'HoursLayoutChanger' and 'TicketPropsLayoutChanger' : enabling these breaks Wysiwyg.
Please try to reproduce it on your side.
Probably this ticket should be relayed to TicketDeletePlugin and TimingAndEstimationPlugin components, but I am reporting it here because for us Wysiwyg is more important and visible in our Trac.
Thank you in advance for your help.