Indicate things to be removed in version 2.0

autoload/ale/engine.vim

@@ -367,6 +367,7 @@ function! ale#engine#SetResults(buffer, loclist) abort
 
         " Call user autocommands. This allows users to hook into ALE's lint cycle.
         silent doautocmd <nomodeline> User ALELintPost
+        " remove in 2.0
         " Old DEPRECATED name; call it for backwards compatibility.
         silent doautocmd <nomodeline> User ALELint
     endif

autoload/ale/statusline.vim

@@ -1,6 +1,8 @@
 " Author: KabbAmine <amine.kabb@gmail.com>
 " Description: Statusline related function(s)
 
+" remove in 2.0
+"
 " A deprecated setting for ale#statusline#Status()
 " See :help ale#statusline#Count() for getting status reports.
 let g:ale_statusline_format = get(g:, 'ale_statusline_format',
@@ -96,6 +98,8 @@ function! s:StatusForListFormat() abort
     return l:res
 endfunction
 
+" remove in 2.0
+"
 " Returns a formatted string that can be integrated in the statusline.
 "
 " This function is deprecated, and should not be used. Use the airline plugin

plugin/ale.vim

@@ -32,6 +32,7 @@ if !s:has_features
     finish
 endif
 
+" remove in 2.0
 if has('nvim') && !has('nvim-0.2.0') && !get(g:, 'ale_use_deprecated_neovim')
     execute 'echom ''ALE support for NeoVim versions below 0.2.0 is deprecated.'''
     execute 'echom ''Use `let g:ale_use_deprecated_neovim = 1` to silence this warning for now.'''
@@ -233,6 +234,7 @@ augroup END
 
 " Backwards Compatibility
 
+" remove in 2.0
 function! ALELint(delay) abort
     if !get(g:, 'ale_deprecation_ale_lint', 0)
         execute 'echom ''ALELint() is deprecated, use ale#Queue() instead.'''
@@ -242,6 +244,7 @@ function! ALELint(delay) abort
     call ale#Queue(a:delay)
 endfunction
 
+" remove in 2.0
 function! ALEGetStatusLine() abort
     if !get(g:, 'ale_deprecation_ale_get_status_line', 0)
         execute 'echom ''ALEGetStatusLine() is deprecated.'''