Template parameters and xml tags in description disappeared with upgrade to 5.1.5

Hi,

Template parameters in description disappeared with upgrade to 5.1.5.
For example:
template<int I, typename T>
struct B
{ };

template<typename T1, typename T2>
struct D : B<1, T1> B<2, T2>
{ };

now shown as:
template
struct B
{ };

template
struct D : B<1, T1>, B<2, T2>
{ };

Same we can see with xml tags - they are disappeared as well...
Is it possible to go back to simple text field?

Does this setting have any impact on the Notes? I've change the field type from mediumtext to varchar(4000) and yet the field is still uses a smart editor.

We have upgraded to 6.0.5 and this problem appeared again despite database fields format still is 'varchar(4000)'.
Please advice ASAP as we cannot use it with this problem!
Editor selection has no effect at all!