Vim displays coloring marks on backspace - vim

Question

Every time I'm in insert mode, when I press backspace, something like on image below happens. On save everything is saved properly, but until then - it looks broken.
It seems like shell colour characters, but I'm not really sure.
After some testing, and removing pieces of .vimrc, seems like it's issue of delimitMate.
What could be the reason?

Answer 1

s:ExtraMappings() defines a map for Backspace in plugin/delimitMate.vim:
" If pair is empty, delete both delimiters:
inoremap <silent> <Plug>delimitMateBS <C-R>=delimitMate#BS()<CR>
if !hasmapto('<Plug>delimitMateBS','i')
if empty(maparg('<BS>', 'i'))
silent! imap <unique> <buffer> <BS> <Plug>delimitMateBS
endif
if empty(maparg('<C-H>', 'i'))
silent! imap <unique> <buffer> <C-h> <Plug>delimitMateBS
endif
endif
Note that <Plug>delimitMateBS is mapped to <C-R>=delimitMate#BS()<CR>. <C-R>= enters an expression, and that expression will be returned by delimitMate#BS(). See :help c_CTRL-R_=:
'=' the expression register: you are prompted to
enter an expression (see expression)
delimitMate#BS() returns key inputs to handle pairs in autoload/delimitMate.vim:
function! delimitMate#BS() " {{{
if s:is_forbidden("")
let extra = ''
elseif &bs !~ 'start\|2'
let extra = ''
elseif delimitMate#WithinEmptyPair()
let extra = "\<Del>"
elseif s:is_space_expansion()
let extra = "\<Del>"
elseif s:is_cr_expansion()
let extra = repeat("\<Del>",
\ len(matchstr(getline(line('.') + 1), '^\s*\S')))
else
let extra = ''
endif
return "\<BS>" . extra
endfunction " }}} delimitMate#BS()
By looking into the code, you can know the return value can be:
"\<BS>"
"\<BS>\<Del>"
"\<BS>\<Del>\<Del>"
…
So as I think, it's an issue of handling Backspace or Delete. See :help :fixdel for additional information.
:fix[del] Set the value of 't_kD':
't_kb' is 't_kD' becomes
CTRL-? CTRL-H
not CTRL-? CTRL-?
(CTRL-? is 0177 octal, 0x7f hex) {not in Vi}
If your delete key terminal code is wrong, but the
code for backspace is alright, you can put this in
your .vimrc:
:fixdel
This works no matter what the actual code for
backspace is.
If the backspace key terminal code is wrong you can
use this:
:if &term == "termname"
: set t_kb=^V<BS>
: fixdel
:endif
Where "^V" is CTRL-V and "<BS>" is the backspace key
(don't type four characters!). Replace "termname"
with your terminal name.
If your <Delete> key sends a strange key sequence (not
CTRL-? or CTRL-H) you cannot use ":fixdel". Then use:
:if &term == "termname"
: set t_kD=^V<Delete>
:endif
Where "^V" is CTRL-V and "<Delete>" is the delete key
(don't type eight characters!). Replace "termname"
with your terminal name.