thanks for the kind words on 5.0!
telling you how to do this would be a lot easier when we get our codex documents in place… 
actually, that isnt the page you want… and you dont want to change the core code… the new api lets your remove things just like in wp with filters… you can see the available filters in the codex, but they are not fully defined… so the file is sp-form-profile.php, but we dont want to edit it – only look at it for the filters we want to use to remove stuff…
but not sure why you want to remove those items… they are information only.. and you can disable users from changing their display name on forum – profiles – profile options… and they already cannot change their login name – just view it which they already know since they logged in… and this is the profile edit page, so its not visible to other users anyways…
but if you want to remove from the edit profile page, lets start with an example – the login name… in that code, around line 50 you will see it displayed (actually just stored in temp variable)… a couple of lines later you will see an apply_filters() function call… this lets you change what gets output… in this case, remove…
so… in your functions.php in the sp theme, you would do something like this:
add_filter('sph_ProfileUserLoginName', 'myremovelogin');
function myremovelogin($out) {
return '';
}
this will now remove the login name from the edit profile page… the add_filter() function says when sp fires the hook sph_ProfileUserLoginName, call my function myremovelogin() and execute my code… in this code, replace the existing output with an empty string – which removes from the form… the things you could do there are pretty much limitless…
and then repeat for the other filters on the profile items: sph_ProfileUserDisplayName, sph_ProfileUserFirstName, sph_ProfileUserLastName obviously adding a new function name in the add_filter() for each…
this may seem strange and a bit odd to get used to, but its the standard wp api and way of doing things…
and will be easier to do than looking through code when we get our codex populated… all hooks/actions/filters will be documented so you can see what is possible…