From the previous version of my last post, people with even moderate knowledge of English could have easily understood that I suck at spelling and that, consequently, I did not have a spelling checker installed at this blog. Both of those two conclusions would be true.
So I decided to break in and install something to help me and after some mishaps, I settled on Visual Spellcheck plug-in. I am editing my posts in HTML anyway, so lack of WYSIWYG editor support is not critical for me, more like the opposite. All I needed was to install the plug-in, activate it in wordpress, install php5-pspell package and restart Apache. I forgot to restart Apache at first and got a cryptic error from the included fake pspell wrapper. Also aspell and corresponding language libraries must be installed on server site.
Note: after you have corrected all spelling errors in your text you must also remember to press "Continue Editing" link or otherwise changes will not be saved. I think that is a bug.