Deselecting balanced tags doesn't have much advantage (apart from enabling the fake xp nodelet on g0n's homenode), I think it's a historical feature. On the other hand, deselecting "HTML error reporting during preview", which shows the unbalanced tags and other HTML errors as grey tags can have an advantage if you write HTML using all the optional opening and closing tags the standard allows, because then perlmonks keeps complaining about unclosed tr, th, td, li, dt, dd tags (you don't ever need to close those though you can: a tr is closed by the next tr or closing the table, a th or td is closed by the next tr, td, td, or the end of the table, etc). It sometimes even complains about a missing closing p tag, like when a p tag is inside a blockquote or readmore. All those grey tags in the preview can be annoying if you mostly write correct HTML anyway.